HANDBOOK 

FOR 

HEATING  AND  VENTILATING 
ENGINEEES 


BY 

JAMES  D.  HOFFMAN,  M.  E. 

PROFESSOR   OF   MECHANICAL   ENGINEERING   AND    PRACTICAL 

MECHANICS,    UNIVERSITY   OF   NEBRASKA 

MEMBER    AND    PAST    PRESIDENT    A.    8.    H.    &   V.    E. 

MEMBER   A.    8.    M.    E. 

ASSISTED  BY 

BENEDICT  F.  RABER,  B.  S.,  M.  E. 

ASSISTANT   PROFESSOR   OF    MECHANICAL    ENGINEERING 
UNIVERSITY   OF   NEBRASKA 


McGRAW-HILL   BOOK   COMPANY 

239  WEST  39TH  STREET,  NEW  YORK 

6  BOUVERIE  STREET,  LONDON,  E.  C. 

1913 


COPYRIGHT,  1913 

BY 
JAMES  D.  HOFFMAN 


(First  Edition:  Copyright,  1910, 
By  James  D.  Hoffman) 


EXTRACT    FROM    PREFACE    TO    FIRST    EDITION. 

In  the  development  of  Heating  and  Ventilating  work,  it 
is  highly  desirable  that  those  engaged  in  the  design  and  the 
installation  of  the  apparatus  be  provided  with  a  hand-book 
convenient  for  pocket  use.  Such  a  treatise  should  cover  the 
entire  field  of  heating  and  ventilation  in  a  simplified  form 
and  should  contain  such  tables  as  are  commonly  used  in 
every  day  practice.  This  book  aims  to  fulfill  such  a  need  and 
is  intended  to  supplement  other  more  specialized  works.  Be- 
cause of  the  scope  of  the  work,  its  various  phases  could  not 
be  discussed  exhaustively,  but  it  is  believed  that  all  the  fun-  • 
damental  principles  are  stated  and  applied  in  such  a  way  as 
to  be  easily  understood.  It  is  suggestive  rather  than  diges- 
tive. The  principles  presented  are  the  same  as  those  that 
have  been  stated  many  times  before,  but  the  arrangement  of 
the  work,  the  applications  and  the  designs  are  all  original. 
Many  formulas  and  rules  are  necessarily  given;  but  it  will 
be  seen  that,  in  most  cases,  they  are  developments  from  a  few 
general  formulas,  all  of  which  can  be  readily  understood  and 
remembered.  Practical  points  in  constructive  design  have 
also  been  considered.  However,  since  the  principles  of  heat- 
ing and  ventilation  are  founded  upon  fundamental  thermo- 
dynamic  laws,  it  seems  best  to  accentuate  the  theoretical 
side  of  the  work  in  the  belief  that  if  this  is  well  understood, 
practical  points  of  experience  will  easily  follow.  A  pamphlet 
containing  suggestions  and  problems  for  a  course  of  instruc- 
tion in  technical  schools  is  included  with  every  book. 

It  is  hoped  that  the  material  here  given  will  be  simple 
enough  for  the  beginner  and,  at  the  same  time,  sufficiently 
complete  and  exact  for  the  engineer  with  years  of  experience. 
If  it  merits  the  approval  of  the  reader,  or  if  any  part  is  de- 
fective or  misleading,  we  trust  that  statements  of  criticism 
will  be  freely  contributed.  The  only  way  to  perfect  such  a 


book  is  to  have  the  good  wishes  and  the  co-operation  of  en- 
gineers in  all  branches  of  the  work.     These  are  solicited. 

All  the  standard  works  upon  the  subject  have  been  freely 
consulted  and  used.  In  most  cases  where  extracts  are  made, 
acknowledgment  is  given  in  the  text.  In  addition  to  this, 
references  for  continued  reading  are  quoted  at  the  close  of 
each  important  topic.  Because  of  these  references  through- 
out the  book,  we  do  not  here  repeat  the  names  of  their 
authors.  We  wish,  however,  to  express  our  sincere  apprecia- 
tion of  their  valuable  assistance. 

J.   D.  H. 


PREFACE    TO    SECOND   EDITION. 

•The  demand  for  copies  of  the  first  edition  of  the  hand- 
book was  so  great  as  to  make  a  second  edition  necessary 
within  the  second  year  after  publication  of  the  first  edition. 
A  few  corrections  were  made  on  the  first  edition  and  all 
the  material  has  been  revised  to  bring  it  up  to  date.  The 
work  on  air  conditioning  has  been  amplified.  The  descrip- 
tions of  hot  water  and  steam  heating  have  been  improved 
by  diagrams  of  the  various  piping  systems.  Two  chapters 
have  been  added  on  refrigeration  and  many  tables  have 
been  added  in  the  Appendix.  Many  suggestions  have  come 
from  men  in  practice  and  these  suggestions  have  been  con- 
sidered, thus  enlarging  upon  the  practical  side  and  the  ap- 
plications. It  is  believed  now  that  every  subject  discussed 
within  the  -scope  of  the  book  has  been  revised  to  meet  the 
present  state  of  the  science. 

Lincoln,  Neb.  J.  D.  H. 


CONTENTS 


CHAPTER  I.      (Heat) 

Arts.  Pages 
1-     4^  Introductory.       Measurement     of     Heat    and 

Temperatures     9-  13 

5  Radiation,  Conduction,  Convection    14-   15 

CHAPTER  II.      (Air) 
6-     9     Composition    of    Air.      Amount    Required    per 

Penson    16-  24 

10-   13     Humidity     25-   30 

14-   15     Comvection  of  Air.     Measurement  <of  Air  Ve- 
locities      31-   34 

16-  20'     Air  Used  in  Combustion.     Chimneys 35-   37 

References  on  Ventilation 38 

CHAPTER  III.      (Heat  Losses) 

21-   29     Heat  Losses   from  Buildings    39-   47 

30  Temperatures  to  be  Considered    47-   48 

31  Heat  given  off  from  Lights  and  Persons....  49 
References  on  Heat  Losses  from  Buildings.  .  50 

CHAPTER  IV.     (Furnace  Heating) 

32-   34     Essentials  of  the  Furnace  System 51-   53 

35-   37     Air  Circulation  in  Furnace  Heating 53-   55 

38-   47     Calculations   in   Furnace   Design    56-   61 

48  Application  to  a  Ten  Room  Residence 62-   66 

CHAPTER  V.     (Furnace  Heating,  Continued) 

49-   51     Selecting,  Locating  and  Setting  the  Furnace  67-  71 

52-  57     Air  Ducts.     Circulation  of  Air  in  Rooms....  71-  76 

58  Fan-Furnace   Heating    77 

59  Suggestions  for  Operating  Furnaces 78-  79 

60  Best  Outside  Temperature    79-  83 

References  on  Furnace  Heating 84 

CHAPTER  VI.      (Hot  Water  and   Steam   Heating) 

61-   66     Comparison  and  Classification  of  Systems...  85-   90 

67  Diagrams  of  Piping  Systems 91-  95 

68  Accelerated  Systems   95-  99 

69  Vacuum  Systems  for  Steam   99-102 

CHAPTER  VII.      (Ht.   Water  and  St.   Heating,   Cont'd) 
70-   75     Classification  and  Efficiencies  of  Radiators.  .103-108 
76-  79     Heaters  and  Boilers.     Combination  Systems. 

Fittings    108-113 


CHAPTER  VIII.      (Ht.  Water  and  St.  Heating  Cont'd) 
Arts.  Pages 

80-   83     Calculation   of  Radiator  Surface    114-121 

83-   86     Pipe  Sizes.    Grate  Area.    Piping  Connections.  121-124 
84  General  Application  to  Hot  Water  Design.  .  .125-131 

88-   89     Insulating  Steam  Pipes.     Water  Hammer.  .  .131-133 

90  Feeding  Return  Wiater  to  Boiler 133-137 

91  Suggestions  for  Operating  Boilers 137-138 

References  on  Hot  Water  and  Steam  Heat'g  139-140 

CHAPTER   IX.      (Mechanical    Vacuum    Heating) 
92-   96     General.      Webster,    Van    Auken,    Automatic 

and  Paul  Systems 141-151 

97  References  on  Mechanical  Vacuum  Heating  152 

CHAPTER  X.      (Mechanical  Warm  Air  Heating) 
98-104     General      Discussion.        Blowers     and      Fans. 

Heating  Surfaces   153-165 

105-107  Single  and  Double  Duct  Systems.  Air  Wash- 
ing   165-168 

CHAPTER  XI.     (Mech.  Warm  Air  Heating,  Cont'd) 

108-112  Heat  Loss.  Air  Required.  Air  Tempera- 
tures   169-172 

113-114     Air  Velocities.     Area  of  Ducts 172-173 

115-120  Heating  Surface  in  Coils.  Arrangement  of 

Coils  173-183 

121-122     Amount  of  Steam  Used  in  the  System 183 

CHAPTER  XII.      (Mech.  Warm  Air  Heating,  Oont'd) 

123-129     Air  Velocity  and  Pressure.     Horse-Power  in 

Moving   Air    184-195 

130-133     Fan  Drives.    Speeds.     Size  of  Engine.    Piping 

Connections    195-200 

134  General  Application  to  Plenum  System 200-205 

References    on    Mechanical    Warm    Air   Heat- 
ing   .  . .206-207 

CHAPTER  XIII.      (District  Heating) 
135-139     General.         Conduits.         Expansion       Joints. 

Anchors    208-222 

140-14)2     Typical  Design.     Heat  in  Exhaust  Steam.  ..  .222-228 
143-146     Hot  Water  Systems.     General  Discussion.  .  ..229-231 

147-149     Pressure  and  Velocity  of  Water  in  Mains 231-235 

150-154     Radiation   Heated  toy  Exhaust   Steam 236-238 

155-160     Reheating  Calculations    238-244 

161-164     Circulating  Pumps.     Boiler  Feed  Pumps 244-251 

165-169  Radiation  Supplied  by  Boilers  and  Economiz- 
ers  251-255 

170  Total  Capacity  of  Boiler  Plant 255-258 

171-173     Cost  of  Heating  from  Central  Station 258-263 

174  Steam  System.     General  Discussion    264-265 


Arts.  Pages 

175-177     Pipe  Sizes.     Dripping  the  Mains 265-267 

178              General  Application  of  Steam  System  to  Dis- 
trict      268-269 

References  on  District  Heating   270 

CHAPTER  XIV.      (Temperature  Control) 
179-182     General.     Johnson,  Powers  and  National  Sys- 
tems       271-279 

CHAPTER  XV.      (Electrical  Heating) 

183-185     Discussion   and  Calculations    280-282 

CHAPTER  XVI.      (Refrigeration) 

186-187     Discussion  of  Systems    283-284 

188-189     Vacuum  and  Cold  Air  Systems   284 

190-191     Compression  and  Absorption  Systems 285-288 

192  Condensers    289-29,1 

193  Evaporators    292-293 

194  Pipes,  Valves  and  Fittings 294 

195-196     Absorption  System 294-297 

197-198     Generators    298-299 

199-203  Condensers,      Absorbers,      Exchangers      and 

Pumps    299-301 

204-205     Comparison  of  Systems 302 

206  Methods  of  Maintaining  Low  Temperatures  303-305 

207  Influence  of  Dew  Point   305 

208  Pipe  Line  Refrigeration    306-307 

CHAPTER  XVII.     (Refrigeration,  Gont'd) 

210-212     Calculations    308-312 

213-216     General  Application    313-315 

217  Cost  of  Refrigeration 316-317 

References  on  Refrigeration    318 

CHAPTER  XVIII.     (Specifications) 

218  Suggestions  on   Planning  Specifications 319-325 

APPENDIX. 
Tables  and  Diagrams 327 


CHAPTER  I. 


HEAT — ITS  NATURE,  GENERATION,  USE,  MEASUREMENT 
AND  TRANSMISSION. 


1.  Introductory: — In  all  localities  where  the  atmosphere 
drops  in  temperature  much  below  60  degrees  Fahrenheit, 
there  is  created  a  demand  for  the  artificial  heating  of  build- 
ings. As  the  buildings  have  grown  in  size  and  complexity 
of  construction,  so  also  this  demand  has  grown  in  extent 
and  preciseness,  with  the  general  result  that  from  the 
antiquated  open  fire-place  and  iron  stove,  there  has  devel- 
oped a  science  growing  richer  each  day  from  inventive 
genius  and  manufacturing  technique — the  science  of  the 
Heating  and  Ventilating  of  Buildings.  The  purpose  of  this 
hand-book  shall  be  to  outline,  concisely,  the  fundamental 
principles  and  practical  applications  of  this  science  in  its* 
various  branches. 

To  the  heating  engineer  of  to-day,  It  may  be  that  the 
exact  nature  of  heat  itself  is  of  much  less  moment  than 
its  generation  and  transmission,  but  this  fact  should  be 
impressed, — that  heat  is  one  form  of  energy,  that  it  cannot 
be  created  except  by  conversion  from  some  other  form,  and 
that  it  is  infallibly  obedient  to  certain  physical  laws  and 
principles. 

In  generating  heat  to-day  for  heating  purposes,  the 
almost  universal  method  is  combustion.  The  union  of  such 
substances  as  coal,  wood  or  peat  with  the  oxygen  of  the 
air  is  always  attended  by  a  liberation  of  heat  derived  from 
the  chemical  action  of  the  combination;  and  this  heat  is 
carried  by  some  common  carrier,  such  as  air,  water  or 
steam,  to  the  building  or  room  to  be  heated  where  it  is  given 
off  by  the  natural  cooling  process.  In  some  instances  this 
heat  is  converted  into  electrical  energy,  which  is  carried  by 
wire  to  the  place  of  use  and  given  off  by  passing  through  a 
set  of  resistance  coils,  which  convert  it  into  heat;  but  this 
method  is  not  much  favored  because  of  its  inefficiency  and 
the  resulting  expense.  This  latter  objection  would  not  hold 
in  the  case  of  water  power  installation,  where  the  combus- 
tion of  fuel  is  entirely  eliminated. 


10  HEATING  AND  VENTILATION 

£.  Measurement  of  Heat:  —  In  the  measurement  of  heat, 
the  most  commonly  accepted  unit  in  practical  engineering 
work  is  the  British  thermal  unit,  commonly  abbreviated  B.  t.  u., 
which  may  be  defined  as  that  amount  of  heat  which  will 
raise  the  temperature  of  one  pound  of  pure  water  one  de- 
gree Fahrenheit,  at  or  near  the  temperature  of  maximum 
density,  39.1°  F.  (See  also  definition  for  Specific  Heat). 
This  unit  value,  the  B.  t.  u.,  measures  the  quantity  of  heat, 
while  the  temperature  measures  the  degree  of  heat.  In 
equal  masses  of  the  same  substance  the  two  are  propor- 
tional. The  Fahrenheit  is  the  more  commonly  used  tem- 
perature scale,  especially  in  steam  engineering.  The  unit  of 
this  scale  is  derived  by  dividing  the  distance  on  the  ther- 
mometer between  the  freezing  point  and  the  boiling  point 
of  water  into  180  equal  degrees,  the  freezing  point  being 
marked  32°,  and  the  boiling  point  212°.  All  temperatures  in 
this  work  will  be  taken  according  to  the  Fahrenheit  scale, 
and  all  quantities  of  heat  expressed  in  British  thermal  units. 

There  is  a  second  unit  of  quantity  of  heat  considerably 
used,  especially  in  scientific  research,  known  as  the  calorie, 
commonly  abbreviated  cal.,  and  defined  as  that  amount  of 
heat  which  will  raise  one  kilogram  of  pure  water  one  de- 
gree Centigrade,  at  or  near  the  temperature  of  maximum 
density,  4°  C.  This  Centigrade  is  a  second  temperature 
scale,  the  unit  of  which  is  derived  by  dividing  the  distance 
on  the  thermometer  between  the  freezing  point  and  the 
boiling  point  of  water  into  100  equal  degrees,  the  freezing 
point  being  marked  0°,  and  the  boiling  point  100°. 

It  is  often  found  desirable  to  change  the  expression  for 
temperature  or  for  quantity  of  heat  from  one  system  of 
terms  to  that  of  the  other.  For  this  purpose  the  following 
formulas  will  be  found  useful: 


and     C=(F  —  32  )  (1) 

where  F  =  Fahrenheit  degrees  and  C  '=  Centigrade  degrees. 
From  these  equations  it  may  be  seen  that  the  two  scales  co- 
incide at  but  one  point,  —  40  degrees.  For  conversion  of  the 
quantity  units  the  following  may  be  used: 

1  British  thermal  unit  =  0.252  Calorie. 

1  Calorie  =  3.968  British  thermal  units. 

These  are  for  the  aibsolute  conversion  of  a  certain  quantity 
of  heat  from  one  system  to  the  other.  If,  however,  the 
effect  of  this  heat  is  considered  upon  a  given  weight  of  sub- 


MEASUREMENT  OF  TEMPERATURE 


11 


Stance  and  the  weight  also  is  expressed  in  the  respective 
systems,  the  following  values  hold: 

1  Calorie  per  kilogram  =  1.8  British  thermal  units  per  pound. 
1  British  thermal   unit  per  pound  =  0.555   Calorie  per  kilo- 
gram. 

Far  conversion  tables  from  kilograms  to  pounds  and  vice 
versa,  see  Suplee's  Mechanical  Engineering  Reference  Book, 
page  72,  or  Kent's  Mechanical  Engineers'  Pocket-Book, 
page  22. 

3.     Measurement  of  High  Temperatures: — For  the  meas- 
urement   of    temperatures    up   to   the   boiling   point   of   mer- 


b. 


Fig.  1. 


Ctiry,  or  approximately  600°  F.,  the  mercurial  thermometer 
of  proper  range  may  be  employed.  It  is  more  common,  how- 
ever, to  use  some  form  of  pyrometer  for  temperatures  above 
500°  F.,  as  when  the  temperatures  of  stack  gases  or  of  fire 
box  gases  are  desired.  Pyrometers  are  built  upon  many  dif- 


12  HEATING  AND  VENTILATION 

ferent  principles,  the  graphite  expansion  stem  type,  shown 
in  Fig.  1,  a;  the  thermo-electric  type,  shown  in  Fig.  1,  b;  or 
the  Siemens  water  calorimeter  type,  shown  in  Fig.  1,  c. 
Various  other  methods  might  be  mentioned,  one  of  the  best 
being  temperature  determination  by  the  Seger  cones,  which, 
due  to  varying  compositions,  melt  at  different  temperatures. 
A  line  of  these  numbered  cones  is  exposed  to  the  sweep  of 
the  gases  to  be  measured,  and  their  temperature  determined 
very  closely  by  noting  the  number  of  the  last  cone  which 
melts.  The  cones  are  numbered  from  022  to  39  and  indicate 
temperatures  from  590°  to  1910°  F.,  by  approximate  incre- 
ments of  20°.  Fig.  1,  d,  shows  cones  010,  09,  08  and  07,  of 
which  only  the  last  is  unaffected,  and,  from  the  table  fur- 
nished with  the  cones,  this  indicates  a  temperature  of  1000°  F. 

4.  Absolute  Temperature: — In  experiments  that  have 
been  carried  on  with  pure  gases  with  the  use  of  air  ther- 
mometers, it  has  been  found  that  air  expands  approximately 
•yj-g-  of  its  volume  per  degree  increase  in  temperature  at 
zero  F.  or  ._!_  of  its  volume  at  zero  C.  From  the  same 
line  of  reasoning,  by  cooling  the  air  below  zero,  the  reverse 
process  should  be  equally  true,  that  is,  for  each  degree 
Fahrenheit  of  cooling  the  volume  at  zero  would  be  contract- 
ed T^F.  Evidently,  then,  if  a  volume  of  gas  could  be  cooled 
to  —  460°  F.,  it  would  cease  to  exist.  This  theoretical  point 
is  called  the  absolute  zero  of  temperature.  All  gases  change 
to  liquids  or  solids  before  this  point  is  reached,  however,  and 
hence  do  not  obey  the  law  of  contraction  of  gases  at  the  very 
low  temperatures.  The  fact  that  air  at  constant  pressure 
changes  its  volume  almost  exactly  in  proportion  to  the  abso- 
lute temperature,  T,  (460  +  t,  where  t  is  temperature  Fahren- 
heit) gives  a  starting  point  to  be  used  as  a  basis  for  all  air 
volume  temperature  calculations.  For  instance,  if  a  volume 
of  20000  cubic  feet  be  taken  in  at  the  air  intake  of  a  build- 
ing at  0°,  and  heated  to  70°,  its  volume,  by  the  heating,  will 
become  greater  in  the  same  proportion  that  its  absolute  tem- 

as  530 

perature  becomes  greater;   that  is,  =  ;  x  =  23000 

20000  460 

cubic  feet,  or  an  increase  of  15  per  cent. 

GAGE  AND  ABSOLUTE  PRESSURES. — Two  common  ways  of  ex- 
pressing pressures  are  in  use.  One  is  denoted  by  the  expres- 
sion pressure  by  gage,  and  refers  to  the  total  pressure  in  a 
container  minus  the  pressure  of  one  atmosphere.  Thus  the 
expression  "65  pounds  boiler  pressure,  by  gage"  means  that 


MECHANICAL    EQUIVALENT    OF    HEAT  13 

the  boiler  is  carrying  65  pounds  pressure,  per  square  inch  of 
surface,  above  the  pressure  of  the  atmosphere,  which  is,  for 
approximate  calculations,  taken  at  the  standard  pressure  of 
14.696  pounds  per  square  inch.  Hence,  the  boiler  carries 
within  it  a  total  pressure  of  65  pounds  plus  14.696  pounds  or 
79.696  pounds  pel  square  inch.  This  total  pressure  is  what 
is  known  as  absolute  pressure,  and  when  stated  in  pounds  per 
square  foot  of  area,  is  called  specific  pressure.  Like  the  volume 
of  a  gas,  so  also  the  absolute  pressure  varies  directly  with 
the  absolute  temperature,  other  things  being  constant.  Hence 
the  equation  P  V  =  R  T,  where  P  is  the  absolute  pressure 
in  pounds  per  square  foot,  V  is  the  volume  of  one  pound  in 
cubic  feet,  T  is  the  absolute  temperature,  and  R  is  a  con- 
stant which  for  air  is  53.22.  From  this  equation,  having 
given  any  two  of  the  quantities,  P,  V  or  T,  the  third  may  be 
found.  In  very  accurate  calculations  where  the  value  14.696 
is  not  considered  close  enough,  the  barometer  may  be  read, 
and  its  readings,  in  inches  of  mercury,  multiplied  by  the 
constant  .49,  to  obtain  the  pressure  of  the  atmosphere  in 
pounds  per  square  inch. 

MECHANICAL  EQUIVALENT  OP  HEAT. — By  precise  experiment,  it 
has  been  determined  that,  if  the  heat  energy  represented  by 
one  B.  t.  u.  be  changed  into  mechanical  energy  without  loss, 
it  would  accomplish  778  foot  pounds  of  work.  Similarly, 
one  calorie  is  equivalent  to  428  kilogrammeters.  One  horse- 
power of  work  is  equivalent  to  the  expenditure  of  33000  foot 
pounds  of  work  per  minute.  Hence  one  horse-power  of 
work  represents  42.416  B.  t.  u.  per  minute. 

LATENT  HEAT. — Not  all  the  heat  applied  to  a  body  pro- 
duces change  in  temperature.  Under  certain  conditions,  the 
heat  applied  produces  internal  or  molecular  changes,  and  is 
called  latent  heat.  Thus  if  heat  is  applied  to  ice  at  the  freez- 
ing point,  no  rise  of  temperature  is  noted  until  all  the  ice 
is  melted;  and  again,  heat  applied  to  water  at  boiling  point 
does  not  raise  the  temperature,  but  changes  the  water  into 
steam.  The  first  is  called  latent  heat  of  fusion,  and  for 
ice  is  142  B.  t.  u.  per  pound,  while  the  latter  is  called  latent 
heat  of  evaporation,  and  for  water  is  969.7  B.  t.  u.  per  pound. 

SPECIFIC  HEAT. — The  ratio  of  the  quantity  of  heat  required 
to  raise  the  temperature  of  a  substance  one  degree,  to  that 
required  to  raise  the  temperature  of  the  same  weight  of 
pure  water  one  degree  from  the  temperature  of  its  maxi- 
mum density,  39.1  degrees,  is  commonly  called  the  specific 
heat  of  the  substance.  The  above  is  the  accepted  rule  among 


14  HEATING  AND  VENTILATION 

physicists.  This,  however,  has  been  modified  by  engineering 
practice  so  that  the  statement  specific  heat  of  water  is  now 
understood  to  mean  the  average  specific  heat  erf  water  be- 
tween 32  degrees  and  212  degrees.  (Amount  of  hea.t  neces- 
sary to  raise  one  pound  of  water  from  32  degrees  F.  to  212 
degrees  F.)  -j-  180  —  1  approximately.  Table  24,  Appendix, 
gives  specific  heats  of  substances. 

5.  Radiation,  Conduction  and  Convection: — -The  transmis- 
sion of  heat,  next  to  its  generation,  forms  an  item  of  vital 
interest  to  the  heating  engineer,  for  different  forms  of  heat- 
ing installations  are  based  fundamentally  on  the  different 
ways  in  which  heat  is  transmitted.  These  ways  are  usually 
quoted  as  being  three  in  number — radiation,  conduction  and 
convection. 

RADIATION. — This  transmission  of  heat  occurs  as  a  wave 
motion  in  the  ether  of  space,  and  is  the  way  by  which  the 
heat  of  the  sun  reaches  the  earth.  Heat  of  this  form,  usu- 
ally referred  to  as  radiant  heat,  requires  no  matter  for  its 
conveyance,  passes  through  some  materials,  notably  rock- 
salt,  without  change  or  appreciable  loss,  and  travels,  as  does 
light,  at  the  rate  of  186000  miles  per  second.  In  the  combus- 
tion of  fuel  the  radiant  heat  given  off  to  the  surrounding 
metal  from  the  rays  o.f  the  fire  is  no  doubt  of  much  greater 
value  than  has  ever  been  credited  to  it.  We  are  indebted 
to  the  noted  French  physicist,  L.  Ser,  who  followed  Peclet 
in  his  experiments  in  radiant  heat  in  fire  box  boilers,  for  a 
very  valuable  amount  of  information.  It  is  to  be  hoped 
that  further  experimentation  may  soon  see  the  relation  be- 
tween  the  "heat  radiated  from  the  incandescent  surface  of 
the  fuel"  and  the  "sensible  heat  in  the  escaping  gases." 
This  would  be  of  great  value  to  those  engaged  in  the  design 
and  operation  of  boiler  furnaces. 

CONDUCTION. — The  second  method  of  transmission  is  more 
commonly  evident  to  the  senses.  If  a  rod  of  metal  is  heat- 
ed at  one  end,  it  is  known  that  the  heat  is  transferred,  or 
conducted,  along  the  rod  until  the  other  end  becomes  heated 
also.  Conduction  being,  essentially,  the  way  by  which  solids 
transfer  heat,  is  hence  of  special  significance  in  the  calcu- 
lation of  heat  losses  through  the  walls  of  a  building.  Rel- 
ative conductivity  of  a  substance  may  be  defined  as  the  quantity 
of  heat  which  passes  through  a  unit  thickness  of  the  sub- 
stance in  a  unit  of  time  across,  a  unit  of  surface  of  the  sub- 
stance, the  difference  of  temperature  between  the  two  sides 
of  the  substance  being  one  unit  of  the  thermometric  scale 


HEAT    TRANSMISSION 


15 


Fig.   2. 


employed.  Since  the  complexity  of  our  building  construc- 
tions renders  it  obviously  impossible  to  reduce  all  losses  to 
losses  per  unit  thickness  of  the  structure,  we  are  not  per- 
mitted to  use  the  term  "relative  conductivity"  but  another 
term,  i.  e.,  "transmission  constant,"  or  rate  of  transmission. 
Thus  Table  IV,  page  40,  the  rate  of  transmission  K,  given 
for  a  6  inch  studded  frame  wall,  is  .25  B.  t.  u.  per  square 
foot  of  surface  per  degree  difference  of  temperature  for  one 
hour.  It  is  readily  seen  that  this  table  is  the  basis  for  the 
heat  loss  calculations  of  buildings. 

CONNECTION. — Gases  and  liquids  convey  heat 
most  readily  by  this  method,  which  is  funda- 
mental with  hot  air  and  hot  water  heating 
installations.  If  it  is  attempted  to  heat  a 
body  of  water  by  applying  heat  to  its  upper 
surface,  it  will  be  found  to  warm  up  with 
extreme  slowness.  If,  however,  the  source  of 
heat  be  applied  below  the  body  of  water  as 
in  Fig.  2,  it  will  be  found  to  heat  rapidly,  the 
water  being  distributed  by  circulating  cur- 
rents having  more  or  less  force,  and  follow- 
ing, in  general,  the  direction  shown  by  the  ar- 
rows. What  actually  'happens  is  this: — water 
particles  near  the  source  of  heat  become  lighter, 
volume  for  volume,  than  the  colder  particles 
near  the  top;  then,  because  of  the  change  in 
density,  gravity  causes  an  exchange  of  these 
particles,  drawing  the  heavier  to  the  bottom  and 
allowing  the  heated  and  lighter  particles  to  rise 
to  the  top,  thus  forming  the  circulation  currents. 
This  process  is  known  as  convection.  It  will 
never  occur  unless  the  medium  expands  con- 
siderably upon  being  heated,  and  unless  the 
force  of  gravity  is  free  to  establish  circulating 
currents.  The  hot  water  heating  system  may 
be  considered  merely  as  a  body  of  water,  Fi^g.  3, 
furnished  with  proper  pipe  circuits.  When 
heated  at  one  point,  the  water  rises  by  convec- 
tion to  the  radiators,  is  there  cooled,  hence  be- 
comes heavier,  and  descends  by  the  return  cir- 
cuit to  the  point  of  heat  application,  thus  completing  the 
circuit.  The  warm  air  furnace  installation  works  similarly, 
air,  however,  being  the  heat-carrying  medium. 


n 


Fig.   3. 


CHAPTER  II. 


AIR    COMPOSITION — VENTILATION     HUMIDITY. 


6.  Composition  of  Atmospheric  Air: — The  subject  of 
ventilation  as  applied  to  buildings  would  naturally  be  in- 
troduced by  a  brief  consideration  of  the  properties  of  the 
air  supplied.  This  supply  is  a  very  important  factor  as  re- 
gards both  quality  and  quantity.  In  addition  to  its  value 
as  a  heating  medium,  it  determines,  in  a  large  measure,  the 
health  of  the  occupants  of  the  building. 

The  human  body  may  be  considered  as  a  well  equipped 
and  very  complex  power  plant.  As  the  carbon,  hydro- 
gen and  oxygen  in  the  fuel  and  air  supply  in  any  mechan- 
ical power  plant  are  consumed  in  the  furnace,  the  resulting 
heat  absorbed  in  the  generating  system  and  finally  turned 
into  work  through  the  attached  mechanisms,  so  the  human 
body  in  a  similar  way,  but  at  a  much  slower  rate,  absorbs 
the  heat  of  combustion  and  turns  it  into  work.  The  prod- 
ucts of  combustion  in  both  cases  are  largely  carbon  dioxide 
and  water.  The  chief  requisites  of  the  mechanical  plant 
are  good  fuel,  good  draft  and  good  stoking.  Similarly,  the 
human  body  needs  pure  food,  pure  air  and  healthful  exer- 
cise. Of  the  three,  the  second  is  probably  of  the  greatest 
importance,  since  no  person  can  keep  in  health  with  im- 
pure air,  even  though  accompanied  with  the  best  of  food 
and  plenty  of  exercise. 

Air,  to  the  average  person,  is  made  up  of  two  elements, 
oxygen  and  nitrogen,  in  the  volume  ratio  of  about  20.9  to 
79.1  and  a  density  ratio  of  about  23.1  .to  76.9,  respectively. 
We  find  in  making  a  complete  analysis  of  pure  air,  that  a 
number  of  other  elements  and  compounds  enter  into  it,  mak- 
ing a  mechanical  mixture  which  is  somewhat  complex.  To 
the  heating  and  ventilating  engineer,  however,  two  im- 
portant substances  must  be  added  to  the  two  just  stated, 
and  a  revision  of  the  percentages  will  therefore  be  neces- 
sary. It  may  be  said  that  pure  air,  as  taken  from  the  good 
open  country  and  not  contaminated  with  poisonous  gases 
or  the  dust  and  refuse  from  the  cities,  would  have  about 


COMPOSITION    OF    AIR  17 

the    following    composition.      See     Encyclopedia     Britannica, 

Respiration. 

Oxygen  Symbol  O  Per  cent,  of  volume  20.26 

Nitrogen  "         N  ' 78.00 

Moisture  "         H2O  1.7 

Carbon  dioxide  "         CO2  "  .04 

These  values  are  fairly  constant,  except  that  of  the  mois- 
ture, which  may  vary  according  to  the  humidity  anywhere 
from  0  +  to  4  per  cent,  of  the  entire  weight  of  the  air.  In 
places  where  the  air  is  not  pure,  the  following  substances 
may  be  found  in  small  quantities:  carbon  monoxide  (CO), 
sulphuretted  hydrogen  (H2S),  ozone,  argon,  compounds  of 
ammonia,  and  compounds  of  nitric,  nitrous,  sulphuric  and 
sulphurous  acids. 

In   the   process    of   respiration,    the   lungs  and    the   skin 
of   the   average   person   will   change   the   composition    of   the 
air  film  around  the  person  from  that  given  above  to 
Oxygen  Per  cent,  of  volume  16 

Nitrogen  "  "     .     "          75 

Moisture  5 

Carbon  dioxide  4 

Comparing  these  values  with  'those  for  pure  air,  it  will 
be  seen  that  the  oxygen  has  been  reduced  about  one-fifth, 
the  nitrogen  has  been  reduced  about  one  twenty-fifth,  the 
vapor  has  increased  three  times  and  the  carbon  dioxide  has 
increased  one  hundred  times.  Oxygen  has  been  consumed 
in  its  uniting  with  the  excess  carbon  and  hydrogen  in  the 
(System,  and  is  given  off  as  carbon  dioxide  and  water  vapor. 
It  may  be  seen  from  these  ratios,  that  the  very  rapid  increase 
in  CO2  and  the  accompanying  impurities  of  animal  matter, 
would  soon  render  unfit  for  use  the  air  in  almost  any  build- 
Ing  occupied  by  a  number  of  people.  To  avoid  this  state  of 
affairs,  fresh  -air  should  be  supplied  continuously  and  at 
such  points  as  will  provide  the  mo-st  uniform  circulation. 

7.  Oxygen  and  Nitrogen: — The  oxygen  of  the  air  fills 
about  one-fifth  of  the  volume  in  atmospheric  air  and  is  the 
element  that  makes  combustion  possible.  The  other  four- 
fifths  of  the  space  might  be  said  to  be  filled  with  nitrogen. 
In  a  providential  way,  this  nitrogen  acts  as  a  sort  of  buffer 
in  its  mixture  with  the  oxygen  and  serves  to  control  the 
rapidity  with  which  the  combustion  takes  place.  Nitrogen 
seems  to  have  little  effect  upon  the  respiration,  except  to 


18  HEATING  AND  VENTILATION 

retard  the  chemical  action  between  the  oxygen  and  carbon 
and  the  oxygen  and  hydrogen.  If  one  were  to  attempt  to 
live  in  an  atmosphere  of  pure  oxygen,  the  chemical  action 
in  the  lungs  would  be  so  rapid  that  the  human  body  would 
not  be  able  to  maintain  it. 

8.  Carbon  Dioxide: — The  amount  of  CO2  in  the  air  is 
used  as  an  index  to  the  purity  of  the  air.  This  is  not  con- 
sidered a  poisonous  gas.  It  has  slight  taste  and  odor  but  no 
color.  It  is  found  in  many  natural  waters  and  manufac- 
tured beverages,  the  chief  one  being  "soda  water,"  which  is 
made  by  forcing  carbon  dioxide  into  water  under  pressure. 
The  real  action  of  CO2  w.hen  taken  into  the  lungs  is  not 
well  known.  It  has  the  effect  of  producing  physical  depres- 
sion, and  where  found  in  sufficient  quantity  would  even  cause 
death  by  suffocation,  very  similar  to  a  submergence  in 
water.  Whatever  its  effect  upon  human  life  may  be,  its  pres- 
ence in  any  room  used  for  habitation  is  usually  an  indica- 
tion of  the  lack  of  oxygen  and  an  excess  of  impurities  thrown 
off  by  respiration.  Pure  air  has  four  parts  CO2  in 
10000  parts  of  air,  and  room  air  'Should  never  be 
allowed  to  have  more  than  eight  -to  ten  parts  in  10000  parts 
of  air.  It  becomes  the  problem  of  the  heating  engineer, 
therefore,  to  provide  air  in  sufficient  quantities,  and  to  enter 
and  withdraw  the  air  from  the  room  in  a  manner  such  as 
will  not  be  uncomfortable  to  the  occupants,  at  the  same 
time  keeping  the  air  fairly  uniform  in  quality,  throughout 
the  room.  Carbon  dioxide  in  the  exhaled  breath  is  about  2.5 
times  heavier  than  air  of  the  same  temperature,  and  there- 
fore would  have  a  tendency  to  fall.  It  is  exhaled,  however, 
with  excessive  moisture  and  at  a  temperature  hdgher  -than 
that  of  the  room  air,  both  qualities  giving  it  a  tendency  to 
rise.  These  latter  factors  probably  neutralize  the  excessive 
density,  and  as  long  as  the  air  is  not  absolutely  quiet,  would 
eventually  result  in  a  fair  diffusion  throughout  the  room 
air.  In  large  audiences  the  heat  given  off  from  the  occu- 
pants is  sufficient  to  cause  strong  air  currents  which,  in 
rising,  lift  thiis  impure  air  to  the  upper  part  of  the  room. 
In  most  systems  the  vitiated  air  is  withdrawn  from  the 
room  near  the  floor  line.  If,  as  is  urged  by  some,  the  ven- 
tilating air  enters  near  the  floor  line  and  is  removed  from 
the  upper  part  of  the  room  near  the  ceiling,  the  problem 
of  heating  the  room  will  be  more  difficult  and  expensive. 


DETERMINING   THE    PURITY   OF   AIR  19 

The  circulation  of  air  within  rooms  is  being  given  much  at- 
tention now  and  it  is  hoped  that  some  conclusive  results 
may  .soon  be  obtained.  There  is  no  doubt  that  less  air  will 
be  needed  for  proper  ventilation  if  it  is  entered  and  removed 
in  such  a  manner  and  from  such  parts  of  the  room  as  will 
keep  all  the  air  within  the  room  constantly  moving  and  yet 
free  from  localized  air  currents. 

A  method  of  determining  the  percentage  of  carbon  dioxide  in  the 
air,  based  upo'n  the  fact  that  barium  carbonate  is  nearly  in- 
soluble in  water,  may  be  performed  as  follows:  Provide 
eleven  bottles  with  rubber  stoppers  having  two  holes  each, 
and  connect  them  continuously  by  glass  and  rubber  tubing, 
so  that  if  suction  be  applied  at  the  first  bottle  of  the  series, 
air  will  be  drawn  in  at  the  last  of  the  series  and  the  same 
air  will  be  passed  through  all.  In  this  way  a  sample  of  the 
air  to  be  tested  may  be  drawn  into  each  bottle.  The  capac- 
ities of  the  bottles  must  be  made  to  be  respectively,  in 
ounces,  23%,  18%,  16%,  14,  9%,  7%,  5%,  4,  3%,  2-%  and  2. 
This  may  readily  be  done  by  partially  filling  with  paraffine. 
Into  each  bottle  is  then  placed  %  ounce  of  a  50  per  cent,  sat- 
urated solution  of  barium  hydrate,  Ba(O  H)2.  More  of  the 
air  to  be  tested  is  drawn  through  the  system  until  assurance 
is  had  that  each  bottle  contains  a  fair  sample.  Each  bottle  is 
then  thoroughly  shaken,  so  that  the  liquid  may  be  brought 
into  good  contact  with  the  air  sample.  If  the  least  turbidity 
or  cloudiness  appears  in  the 

First   or   largest  bottle   indicates    0.04  per   cent.    CO2 

'Second  bottle  indicates  0.06  " 

Third            "  "  0.07  "          "          "     • 

Fourth        "  "  0.08  " 

Fifth            "  "  0.10  " 

Sixth            "  "  0.15  " 

Seventh       "  "  0.20  " 

Eighth       <*  "  0.30  " 

Ninth           "       .  "      '•  .-•  0.40  " 

Tenth           "  "  0.60  "          " 

Eleventh    "  "  0.90  " 

Care  must  be  taken  to  have  a  fair  sample  of  the  air  in 
each  bottle.  The  glass  tubes  through  the  rubber  stoppers 
should  extend  no  farther  than  the  bottom  of  the  stoppers. 
Fig.  4,  a,  shows  four  of  the  bottles  and  their  connections. 


20 


HEATING  AND  VENTILATION 


As  an  example,  suppose  that  the  air  of  a  room  was  tested 
and  that  in  the  first,  second,  third,  fourth,  fifth  and  sixth 
bottles  the  liquid  became  turbid  after  vigorous  shaking. 
Such  room  air  would  have  contained  0.15  per  cent,  of  carbon 
dioxide,  and  would  have  been  considered  quite  unfit  for 
breathing. 


Fig.   4. 

A  second,  less  cumbersome,  and  more  delicate  method  of  testing 
for  the  percentage  of  carbon  dioxide  will  be  described,  as  it 
is  the  method  commonly  used  and  only  requires  compara- 
tively simple  apparatus,  as  shown  in  Fig.  4,  b.  A  bottle  of 
about  6  ounces  capacity  is  fitted  with  a  rubber  stopper  hav- 
ing two  holes.  Through  one  hole  a  glass  tube  is  brought 
from  the  bottom  of  the  bottle,  and  to  the  outer  end  of  the 
tube  is  connected  a  valved  bulb  similar  to  those  found  on 
atomizers.  Into  the  bottle  are  placed  10  cubic  centimeters 
of  .a  solution  made  by  dissolving  .53  grams  of  anhydrous 
sodium  carbonate,  Na2  OO3,  in  5  liters  of  water,  and  adding 
.01  gram  of  phenolphthalein.  The  water  used  must  have  been 
previously  boiled  for  at  least  one  hour  in  an  open  vessel. 
W'ith  the  apparatus  so  prepared,  squeeze  the  bulb,  -thus  forc- 
ing air  from  the  room  through  the  liquid  and  into  the  bot- 
tle. The  open  hole  in  the  rubber  stopper  is  then  closed  with 
the  thumb,  and  the  bottle  shaken  for  twenty  seconds, 
then  another  bulib-full  of  air  is  inserted,  and  again  shaken. 
This  process  is  continued  and  the  number  of  bulbs  of  air 
noted  until  the  red  color  of  the  solution,  due  to  the  phenolph- 
thalein, disappears.  This  number  of  bulb  fillings  is  indica- 
tive of  the  purity  of  the  air  according  to  the  table  below. 
After  such  an  apparatus  is  completed,  it  must  be  calibrated 


DETERMINING  THE   PURITY  OP  AIR  21 

before  being  used.  This  is  done  by  testing  the  number  of 
bulb  fillings  of  pure  country  air  necessary  to  clear  the 
liquid,  which  will  usually  vary  from  40  to  70.  A  new  table 
for  that  special  apparatus  is  then  obtained  from  the  one 
given  below  by  proportion.  In  the  table  given,  this  number 
of  bulb  fillings,  with  purest  country  air,  is  48.  If,  with  the 
apparatus  made  up,  it  is  found  that,  say,  60  bulb  fillings  are 
required,  then  the  proportionate  table  would  be  made  by 
multiplying  the  number  of  bulb  fillings  given  below  by  the 
ratio  of  60  -f-  48,  or  5  to  4.  It  is  important  that  the  bulb  be 
compressed  the  same  amount  for  each  filling,  and  that  the 
shaking  of  the  bottle  and  contents  be  continued  the  same 
length  of  time  after  each  filling,  to  obtain  uniform  results. 


TABLE   I. 

Fillings 

Per  Cent. 

CO2            Fillings 

Per  Cent.  CO2 

48 

.030 

15 

.074 

40 

.038 

14 

.077 

35 

.042 

13 

.08 

30 

.048 

12 

.083 

28 

.049 

11 

.087 

26 

.051 

10 

.09 

24 

.054 

9 

.10 

22 

.058 

8 

.115 

20 

.062 

7 

.135 

19 

.064 

6 

.155 

18 

.066 

5 

.18 

17 

.069 

4 

.21 

16 

.071 

3 

.25 

The  methods  outlined  for  tht  approximate  estimation  of 
CO2  are  satisfactory  for  determining  whether  or  not  ventila- 
ting systems  maintain  a  proper  degree  of  purity  of  air.  If 
exact  percentages  of  CO,  CO2,  O  and  N  are  required,  the  Orsat 
apparatus  must  be  employed,  for  description  of  which  see 
Engineering  Chemistry  by  Stillman,  page  238.  See  also  Car- 
penter, H.  &  V.  B.,  Chap.  II,  and  Hempel's  Gas  Analysis, 
translated  by  Dennis. 

9.  Amount  of  Air  Required  per  Person: — The  need  of  a 
continuous  supply  of  fresh  air  in  our  residences  and  business 
houses  can  scarcely  be  over-estimated.  Health  is  probably 


HEATING  AND  VENTILATION 

the  greate&t  of  all  blessings  and  pure  air  is  absolutely  es- 
sential to  health.  The  average  adult,  when  engaged  in  or- 
dinary indoor  occupations,  will  exhale  about  twenty  cubic 
inches  of  air  per  respiration.  He  will  also  have  sixteen  to 
twenty  respirations  per  minute,  making  a  total  of  400  cubic 
inches  or,  say,  .25  cubic  foot  of  air  exhaled  per  minute.  If 
as  in  Art.  6,  exhaled  air  contains  4  per  cent.  CO2,  then 
the  average  person  will  exhale  60  X  .25  X  .04  =-  .6  cubic  foot 
CO2  per  hour,  (Pettenkofer,  Smith  &  Parker),  which  is  con- 
stantly being  diffused  throughout  the  air  of  the  room,  thus 
rendering  it  unfit  for  use.  If  the  carbon  dioxide  and  the 
other  impurities  could  be  disassociated  from  the  rest  of  the 
air  and  expelled  from  the  room  without  taking  large  quan- 
tities of  otherwise  pure  air  with  it,  the  problems  of  the  heat- 
ing engineer  would  be  simplified,  but  this  cannot  be  done. 
Because  of  this  rapid  diffusion,  it  is  necessary  to  flood  the 
room  with  fresh  air  in  order  that  the  purity  may  be  main- 
tained at  a  safe  value.  The  ideal  conditions  would  be  to 
have  it  the  same  as  that  of  the  outside  air,  but  the  mechan- 
ical difficulties  around  such  a  ventilating  system  would  be  so 
great  as  to  render  it  prohibitive.  The  standard  of  purity 
which  should  be  aimed  at,  and  one,  as  well,  which  may  be 
attained  with  a  first  class  system,  is,  .06  of  one  per  cent. 
CO2,  i.  e.,  six  parts  of  CO2  in  10*000  pants  of  air.  A  system, 
however,  which  maintains  a  standard  of  8  parts  in  10000 
would  be  considered  fairly  satisfactory.  This  may  be  put  in 
a  simple  form  for  calculation. 

Let  Qi  =  cubic  feet  of  atmospheric  air  needed  per  hour 
per  person;  A  =  cubic  feet  of  CO2  given  off  per  hour  per 
person;  n  =  the  standard  of  purity  to  be  maintained  (al- 
lowable parts  of  CO2  in  10000  parts  of  air);  and  p  =  the 
standard  of  purity  in  atmospheric  air,  say,  4;  then 


If  we  wish  to  maintain  a  purity  in  the  room  of  seven 
parts  CO2  in  10000  parts  of  air,  and  pure  air  contains  four 
parts  in  10000,  we  have  Qi  =  .6  -r-  (.0007  —  .0004)  =  2000 
cubic  feet  of  air  per  hour. 

Another  formula,  quoted,  from  Carpenter's  Heating  and 
Ventilating  of  Buildings,  very  similar  to  the  above,  is 

al 


AIR   REQUIRED   PER   PERSON 


23 


where  a  =  the  purity  of  the  exhaled  breath,  say  400  parts 
in  10000,  n  =  the  purity  to  be  maintained  in  the  room  and 
&  =  the  cubic  feet  of  air  exhaled  per  minute.  Substituting, 
as  above, 

Qi  =  (400  X  60  X  .25)  -f-  (7  —  4)  =  2000  cubic  feet. 

Based  upon  .6  cubic  foot  of  CO2  exhaled  per  person  per 
hour,  Table  II  gives  the  amount  of  air  needed  to  maintain 
the  various  standards  of  purity. 

It  should  be  understood  that  no  hard  and  fast  rule  can 
be  given  for  the  air  requirement  per  person.  This,  natur- 
ally, would  be  a  different  amount  when  considering  the 
physical  development  for  each  person  in  health;  it  would 
also  be  different  for  the  same  person  according  to  his  occu- 
pation at  the  time,  sleep  being  the  least,  waking  rest  some- 
what greater,  and  physical  exercise  the  greatest;  but  it 
varies  decidedly  with  the  state  of  the  person's  health,  or  the 
sanitary  value  of  his  surroundings.  According  as  the  degree 
of  purity  is  demanded,  the  air  supply  must  be  increased  to 
suit  it. 

TABLE   II. 
Cubic  Feet  of  Air  per  Person  per  Hour. 


n 

A 

Oi 

6 

.6 

3000 

7 

.6 

2000 

8 

.6 

1500 

9 

.6 

1200 

10 

.6 

1000 

Generally,  it  is  understood  that  the '  average  adult  sub- 
jected to  average  conditions  will  require  1800  cubic  feet  of  air 
per  hour.  The  amount  of  air  needed  for  ventilation  then  in 
most  cases  can  be  represented  by  the  formula  Q'  —  1800  N, 
where  N  =  the  number  of  people  to  be  provided  for. 

The  following  table  quoted  from  Carpenter's  H.  &  V.  B., 
and  from  Morin  in  Encyclopedia  Britannica,  gives  a  fair 
value  for  the  amount  of  air  per  occupant  per  hour,  that 
should  be  supplied  to  rooms  used  for  various  purposes. 


24  HEATING  AND  VENTILATION 

TABLE   III. 

Hospitals,   ordinary   2000-2400  cu.  ft.  per  hour 

epidemic     5000  "     "       "          " 

Workshops,    ordinary    2000  "     " 

unhealthy  trades   ....3500  "     "      "          " 

Prisons    1700  "     "      "         " 

Theaters   1400-1700  "     "      "• 

Meeting  halls   1000-2000  "     "      " 

Schools,  per  child   400-   500  "     "      " 

"     adult    .  .    800-1000 


Recent  practice  would  tend  to  increase  these  values 
somewhat;  especially  those  relating  'to  school  house  ventil- 
ation, where  a  good  estimate  would  be  800  to  1800  respec- 
tively. 

One  ordinary  gas  burner  of  20  candle  power,  using  four 
cubic  feet  of  gas  per  hour,  will  vitiate  as  much  air  as  three 
or  four  people.  Where  many  lamps  are  used,  this  fact 
should  be  taken  into  account. 

In  summing  up  the  subject  of  fresh  air  supply,  it  is  well  to  call 
attention  to  the  fact  that  the  ordinary  running  conditions  of 
any  room  cannot  be  absolutely  determined  by  a  single  test 
for  carbon  dioxide.  Trials  should  be  frequently  made  and 
records  kept.  Upon  one  day  the  conditions  may  be  unusually 
favorable  and  would  show  a  small  'amount  of  CO2  even 
though  a  very  small  amount  of  fresh  air  be  admitted;  while 
on  other  days,  when  the  conditions  are  not  so  favorable,  a 
large  amount  of  fresh  air  would  have  to  be  supplied  to  main- 
tain the  proper  purity  within.  If  the  only  requirement, 
therefore,  governing  the  ventilation  of  buildings  should  be 
that  a  satisfactory  CO2  test  be  passed,  there  would  be  a  large 
opportunity  to  overrate  or  underrate,  as  the  case  may  be, 
the  ventilating  system  of  the  building.  The  only  safe  method 
in  rating  ventilating  systems  is  to  require  a  minimum  air  supply 
in  addition  to  a  maximum  permissible  percentage  of  C0%. 

The  purification  of  air  by  ozonising  it  has  recently  been  advo- 
cated and  by  some  it  is  claimed  to  be  the  real  solution  of 
the  bad  air  problem.  Definite  scientific  data  are  still  lack- 
ing upon  which  to  base  any  authoritative  statements,  al- 
though the  invigorating  effects  of  breathing  ozonized  air 
will  be  testified  to  by  many.  Ozone  is  an  unstable  form  of 


MEASUREMENT   OF   HUMIDITY  25 

oxygen,  probably  containing  a  greater  number  of  atoms  per 
molecule,  and  is  formed  by  passing  air  through  a  highly 
charged  electric  field.  Because  of  its  unstability  as  a  sub- 
stance it  readily  breaks  up  and  becomes  more  active  as  an 
oxidizing  agent  than  oxygen  itself.  In  its  decomposition  a 
part  goes  into  combination  with  substances  in  the  air,  such 
as  carbon  impurities  thrown  off  from  the  human  body,  and 
burns  them  up,  leaving  the  balance  which  is  probably  pure 
oxygen.  If  in  the  future  the  purifying  effects  of  ozone  are 
found  to  substantiate  the  claims  made  by  some,  ventilation 
problems  may  thus  be  readily  solved  by  air  washing  and 
ozonizing. 

10.  Moisture  with  Air: — Moisture  with  the  air  is  a  bene- 
fit to  both  the  heating  and  ventilating  systems  in  any  room. 
Wlith  moisture  in  the  room,  a  person  may  feel  comfortable 
when  the  temperature  is  several  degrees  lower  than  the 
comfortable  temperature  of  dry  air.  Dry  air  takes  up  the 
moisture  from  the  skin.  The  vaporization  of  this  moisture 
causes  a  loss  of  heat  from  the  body,  and  gives  to  the  per- 
son a  sense  of  cold,  which  is  only  relieved  when  the  tem- 
perature of  the  room  is  increased.  Air  space  that  is  fairly 
saturated  with  moisture  will  not  permit  of  much  evaporation 
from  the  skin,  because  there  is  not  much  demand  for  this 
moisture  with  the  air;  consequently  the  body  retains  that 
heat  and  the  person  has  a  sensation  of  warmth  which  is 
only  relieved  by  lowering  the  temperature  of  the  air  of  the 
room.  On  the  other  hand,  at  low  temperatures  the  mois- 
ture with  air  chills  the  surface  of  the  skin  by  convection, 
a  condition  that  is  not  so  noticeable  when  the  air  is  dry. 
It  follows  from  the  above  statement  that  the  range  of  com- 
fortable 'temperatures  is  less  for  moist  air  than  for  dry  air. 

Concerning  the  effect  of  moisture  in  its  relation  to  the 
heating  and  ventilating  of  the  room,  we  may  say  that  thor- 
oughly dry  air  has  not  the  quality  of  intercepting  radiant 
heat;  moisture,  however,  has  this  quality.  Moist  air  has 
also  somewhat  less  weight  than  dry  air  and  is  more  buoyant. 
Because  of  the  possibility  of  storing  up  the  radiant  heat 
within  the  particles  of  moisture,  and,  because  of  its  con- 
vection qualities,  it  serves  as  a  good  heat  carrier  for  the 
heating  system. 

11.  Humidity  of  the  Air: — The  actual  humidity  is  the 
amount  of  mo-isture,  expressed  in  grains  or  in  pounds  per 


26 


HEATING  AND  VENTILATION 


cubic    foot,    mixed    with    the    air    at    any    temperature.      The 
relative  humidity  is  the  ratio  of  the  amount  of  moisture  actu- 
ally with  the  air  divided  by  the  amount  of  moisture  which 
the  same  volume  could  hold  at  the  same  temperature  when 
saturated.      It   is   very  important   that   the   heating   engineer 
be  able  to  add  to  or  to  take  away  from   the  amount  of  the 
moisture   in    the    air    supply    of   any    building.      To    find    the 
amount   of  moisture   that  should   be  added   or   subtracted  in 
any  case,  it  is  first  necessary  to  determine  the  humidity  of 
the    air    current    at    various    points    along    its    course.      This 
may   be  obtained  by  the  aid  of  the  wet  and  dry  bulb  ther- 
mometer or  by  any  one  of  a  number 
of      hygrometers     supplied     by     the 
trade.     The  wet  and  dry  bulb  ther- 
mometer   has    a   -very    simple    appli- 
cation, and  is  probably  in  most  gen- 
eral   use.       The   principle  of   its   ap- 
plication  is  as   follows:   having  two 
thermometers,     Fig.     5,     let     one     of 
them    register    the    temperature    of 
the   room   air,    the    other   one   being 
kept    wet    by   a    cloth    which    covers 
the   bulb  and  projects   into  a  vessel 
filled    with    water,     shown    between 
the    two    thermometers.      If    the    air 
is    saturated   the    two    thermometers 
will    record    the    same    temperature; 
if,  however,  the  air  is  not  saturated 
the   thermometer   readings   will   dif- 
fer  an   amount    depending   upon   the 
humidity.  It  will  readily  be'seen  that 
the      lowering     of     the     mercury     in 

the   wet  thermometer   is   due   to   the   extraction   of   the   heat 
in  vaporizing  the  moisture  from  the  bulb  to  the  air. 

In  taking  readings,  let  the  mercury  find  a  constant  level 
in  each  thermometer  and  then  note  the  difference  in  tem- 
perature between  the  two.  In  Table  11,  Appendix,  at  this 
difference  and  at  the  room  temperature  read  off  the  rela- 
tive humidity;  then  take  from  Table  12,  Appendix,  the 
amount  of  moisture  with  saturated  air  at  the  temperature 
recorded  by  the  dry  thermometer,  and  multiply  this  by  the 
humidity.  The  result  is  the  amount  of  moisture  with  the 
air  per  cubic  foot  of  volume. 


J 


Fig.   5. 


MEASUREMENT  OF  HUMIDITY  27 

APPLICATION. — Room  air,  70  degrees;  difference  in  readings, 
6  degrees.  From  Table  11,  the  humidity  is  72  per  cent. 
From  Table  12,  col.  7,  .72  X  .001153  =  .00083  pounds  per 
cubic  foot. 

To  avoid  the  necessity  for  the  use  of  tables,  various  in- 
struments have  been  designed,  which,  graphically,  give  the 
relative  humidity  directly.  Fig.  6  shows  such  an  instrument, 


Fig.    6. 

.commonly  known  as  the  hygrodeik.  To  find,  by  it,  the  relative 
humidity  in  the  atmosphere,  swing  the  index  hand  to  the 
left  of  the  chart,  and  adjust  the  sliding  pointer  to  that  de- 
gree of  the  wet  bulb  thermometer  'Scale  at  which  the  mer- 
cury stands.  Then  swing  the  index  hand  to  the  right  until 
the  sliding  pointer  intersects  the  curved  line  which  extends 
downward  to  the  left  from  the  degree  of  the  dry  bulb 
thermometer  scale,  indicated  by  the  top  of  the  mercury 
column  in  the  dry  bulb  tube.  At  that  Intersection,  the  in- 
dex hand  will  point  to  the  relative  humidity  on  scale  at  bot- 
tom of  chart.  Should  the  temperature  indicated  by  the  wet 
bulb  thermometer  be  60  degrees  and  that  of  the  dry  bulb 
70  degrees,  the  index  hand  will  indicate  humidity  of  55 


28  HEATING  AND  VENTILATION 

per  cent.,  when  the  pointer  rests  on  the  intersecting  line 
of  60  degrees  and  70  degrees. 

For  accurate  work  any  instrument  of  the  wet  and  dry  &u/6  type 
should  be  used  in  a  current  of  air  of  not  less  than  15  feet  per  second. 

Note. — A  very  elaborate  series  of  experiments  conduct- 
ed by  Mr.  Willis  H.  Carrier  of  Buffalo,  New  York,  and  pre- 
sented as  a  paper  before  the  American  Society  of  Mechan- 
ical Engineers  in  1911,  seems  to  show  a  theoretical  humidity 
under  varying  conditions  of  temperature  somewhat  different 
from  that  obtained  by  the  U.  S.  Weather  Bureau,  which  has 
always  been  considered  as  a  standard.  Tables  11  and  12, 
Appendix,  are  used  as  reference  in  this  book  but  Fig.  A  fol- 
lowing Table  13,  shows  the  variation  between  the  results 
obtained  by  Mr.  Carrier  and  those  obtained  by  the  Govern- 
ment. The  two  charts  Fig.  B  and  Fig.  C  in  addition  to  Fig. 
A  are  extracted  from  Mr.  Carrier's  work  with  his  permis- 
sion. The  co.m'pleteness  with  which  this  data  has  been 
worked  up  permits  almost  any  information  desired  to  be 
obtained  from  these  two  charts. 

12.  For  Close  Approximations  and  to  avoid  calculations, 
the  humidity  chart,  Fig.  7,  may  also  be  used  in  determining 
relative  humidity,  absolute  humidity,  dew  point,  temperature 
of  wet  bulb  and  temperature  of  dry  bulb.  On  the  left  of  the 
chart  is  a  scale  referring  to  horizontal  lines  giving  tempera- 
tures of  the  wet  bulb.  The  scale  on  the  right  hand,  referring 
to  the  lines  curving  downward  from  right  to  left,  is  the  scale 
of  the  room,  or  dry  bulb,  temperatures.  The  scale  along  the 
bottom  of  the  chart  is  one  of  relative  humidity.  The  scale  of 
numbers  up  the  center  of  the  chart  refers  to  the  lines  curving 
downward  from  left  to  right,  and  indicates  the  absolute  hu-: 
midity,  i.  e.,  grains  of  moisture  per  cubic  fo.ot  with  the  air. 
The  use  of  the  chart  may  be  most  readily  understood  by  a 
few  applications. 

APPLICATION. — Given  dry  bulb  70  degrees  and  wet  bulb  60 
degrees.  Determine  relative  humidity,  absolute  humidity, 
temperature  of  dew  point  for  room,  etc.  First,  starting  on 
the  right  hand  scale  at  70,  follow  down  the  line  this  number 
refers  to  until  it  crosses  the  horizontal  line  of  60  degrees, 
wet  bulb  temperature.  From  this  intersection  drop  to  the 
relative  humidity  scale  and  read  there  55  per  cent.  This  may 
be  checked  with  the  table.  To  obtain  the  absolute  humidity 
it  will  be  noticed  that  the  intersection  of  the  70  degree  and 


MEASUREMENT  OF  HUMIDITY 


HYGROMETRIC    CHART 

GIVING 

HYGROMETER  TEMPERATURES.  RELATIVE  HUMIDITY  GRAINS  OF  MOISTURE  PER  CD    FT. 


140 


10         20        30    "   40        60        60        70        80     •  90       100 

RELATIVE  HUMIDITY   IN   PER  CENT. 

Fig.  7. 

NOTE.— Fig.  7  represents  two  charts  in  one.  First:  the  dry  bulb 
temperature  curve,  which  drops  to  the  left,  unites  with  the  wet  bulb 
and  relative  humidity  coordinates.  Second:  the  absolute  humidity 
curve,  which  rises  to  the  left,  unites  with  the  dry  bulb  and  relative 
humidity  coordinates.  This  makes  it  possible  to  use  the  two  charts  ar 
one,  through  the  relative  humidity  scale  which  is  common  to  both- 


30  HEATING  AND  VENTILATION 

55  per  cent.  'Coordinates  shows  4.4  grains  per  cubic  foot.  If  the 
room  .should  cool,  the  absolute  humidity  would  remain  the 
same  until  the  dew  point  is  reached  (neglecting  air  contrac- 
tion), hence,  following  down  the  4.4  grain  line  to  100  per  cent, 
gives  the  room  temperature  as  52  degrees,  showing  that  if  so 
cooled  the  air  would  begin  depositing  moisture  at  this  tem- 
perature. Again  if  the  room  should  heat  to  90  degrees,  the 
relative  humidity  may  be  obtained  by  following  the  4.4 
grain  line  to  its  intersection  with  the  90  degree  coordinate 
line  of  room  temperature,  and  from  this  intersection  dropping 
to  the  relative  humidity  scale,  reading  there  31  per  cent. 
Thus,  'having  given  air  under  any  set  of  conditions,  the 
effect  that  'a  change  in  any  one  of  these  would  have  upon 
the  remaining  may  be  obtained  without  calculations. 

13.  The  Theoretical  Amount  of  Moisture  to  be  Added  to 
Air  so  as  to  Maintain  a  Certain  Humidity: — 'Warm  air  has  a 
much  greater  capacity  for  holding  moisture  than  cold  air. 
According  to  the  law  of  Gay-Lussac,  when  air  is  taken 
at  a  given  outside  temperature  and  heated  for  interior 
service,  the  volume  increases  with  the  absolute  tempera- 
ture. See  Art.  4.  On  the  other  hand  the  humidity  de- 
creases rapidly.  Air  thus  treated  becomes  dry  and  unpleas- 
ant to  the  occupants,  as  well  as  being  detrimental  to  the 
furnishings  of  the  room.  Some  means  should,  therefore,  be 
provided  to  supply  this  moisture  to  the  air  current. 

In  calculating  the  amount  to  be  added,  let  Q  =  volume 
of  air  in  cubic  feet  per  hour  entering  the  room  at  the  reg- 
ister; t  —  its  temperature  in  degrees  and  T  =  (460  +  t)  = 
its  absolute  temperature;  let  Q'  and  Qo  =  the  correspond- 
ing volumes  after  entering  and  before  entering,  with 
*'  and  to  the  temperatures  in  degrees,  and  T'  =  (460  +  t') 
and  To  =  (460  +  to)  the  absolute  temperatures;  also,  let  u' 
and  uo  be  the  humidities,  respectively,  of  the  room  air  and 
the  outside  air.  Then,  from  the  equations 

TQ'  =  T'Q  and  TQo  =  ToQ  (4) 

find  Q'  and  Qo. 

From  Table  10  or  12,  Appendix,  find  the  amounts  of  mois- 
ture M'  and  Mo  in  one  cubic  foot  of  saturated  air  at  the  tem- 
peratures f  and  t0;  multiply  these  by  the  respective  humidi- 
ties and  volumes,  and  the  difference  between  the  two  final 
quantities  will  be  the  amount  of  moisture  required  per  hour 
as  expressed  by  the  formula 

W  =  Q'M'u'  —  QoMoUo  (5) 


MEASUREMENT   OF  AIR  VELOCITIES 


APPLICATION. — Let  Q  =  5000,  t  =  130,  i'  =  70,  to  =  30,  u'  =  .50, 
ico  =  .50,  Mf  =  7.98,  and  Mo  =  1.935,  then 

Q'  =  5000  X  530  -r-  590  =  4490 

Qo  =  5000  X  490  -^  590  =  4154 

W  =  13896  grains,  or  1.983  pounds  per  hour. 
This  means  that  approximately  2  pounds  of  water  would  be 
evaporated   for   every   5000   cubic  feet   of   fresh   air  entering 
the  register  under   the  above  conditions. 

14.      Velocity  in  the   Convection  of  Air   by  the   Applica- 
tion of  Heat: — Let  ho  Fig.  8,  be  the  height  of  the  chimney 

._  £   or    stack.      If    the    temperature    of    the    gases 

within  the  chimney  C  D  be  the  same  as  that 
of    the    entering    air,    then    there    will    be    no 
natural  circulation,  because  the  column  C  D, 
will    just    balance    a    corresponding    column 
A  B  upon  the  outside;  but  if  the  temperature 
of  the   chimney  gases   C  D  and   entering  air 
A  B  be  tc  degrees  and  to  degrees,  respectively, 
the   chimney   gases    being    (tc  —   to)    degrees 
*•    *        *c        greater    than    that    of    the    outside    air,    then, 
upon    entering    the    chimney,    the    gases    will 
become    less    dense    and    expand    an    amount 
proportional     to     the     absolute    temperature. 
With  an  outside  column  of  ho  feet  in  height, 
it  will  then  require  a  column  within,  ho  +  ho 
feet  in  height  to  produce  equilibrium;  in  oth- 
""    er  words,   the   column   of  gas  producing  mo- 
Fig.  8.          tion  in  the  chimney   has  a  height  of  he  feet. 
Asisume,  in  the  system  of  A  B  C  D  E,  that  the 
cross  sections  at  all  points  be  uniform,  then  the  volumes  of 
A  B    (imaginary  column)    and   C  E   (actual   column)    are   to 
each  other  as  their  respective  heights,  I.  e., 
Vo  :  Vo  +  Vc  :  :  ho  :  ho  +  ho,  or  ho  :  460  +  to  :  :  ho  +  he  :  460  +  tc 
From  this  we  obtain  he  (460  +  to)  =  ho  (to  —  to)  and 

ho     (tc   —   to) 


he  = 


(6) 


460  +  to 

Substituting  for  7i  in  the  equation  v  =  V2  gh,  its  correspond- 
ing value  he,  we  have 


=  8.02 


-/ 


(ta  —  to) 


(7) 


460  +  to 

It   is  found   in   practice   that   the  theoretical   velocity  as 
given    by    this    formula    is    never    obtained,    because    of    the 


32  HEATING  AND  VENTILATION 

friction  of  the  sides  of  the  chimney  and  other  causes.  Mr. 
Alfred  R.  Wolff  quoted  the  actual  discharge  from  the  chim- 
ney as  50  per  cent,  of  the  theoretical.  This  estimate  may 
be  fairly  correct  for  chimneys  of  the  larger  sizes,  but  may 
not  be  realized  on  the  smaller  ones  used  in  residences.  As 
the  transverse  area  becomes  smaller,  the  percentage  of  fric- 
tion increases  very  rapidly  and  soon  becomes  the  principal 
factor.  Prof.  Kent  assumes  a  layer  of  gas  two  inches  thick 
next  the  interior  surface  as  being  ineffective.  This,  if  ap- 
plied to  small  cross-sectional  areas,  increases  the  size  of 
the  chimney  rapidly  from  the  calculated  amount. 

When  formula  7  is  applied  to  hot  air  stacks  in  the 
heating  systems,  the  friction  is  much  less  because  of  the 
smooth  interior,  and  the  actual  velocity  of  the  air  should 
reach  60  to  70  per  cent,  of  the  theoretical. 

15.  Measurement  of  Air  Velocities: — See  also  Arts.  123- 
125.  In  ventilating  work  it  is  often  of  the  greatest  impor- 
tance to  determine  air  velocities  accurately.  The  correct  de- 
termination of  the  sizes  of  air  propelling  fans  or  blowers 
depends  upon  the  ability  to  accurately  measure  the  velocity 
of  delivery.  In  acceptance  and  other  tests  this  measurement 
is  equally  important.  However,  no  entirely  satisfactory  and 
trustworthy  method  of  obtaining  this  measurement  has  as 
yet  been  devised. 

The  velocity  of  moving  air  is  most  commonly  measured 
by  means  of  a  vane  wheel  instrument  called  the  anemometer. 
It  consists  essentially  of  a  delicately  pivoted  wheel  holding 
from  6  to  15  vanes  and  similar  to  the  common  wind-mill 
wheel.  See  Fig.  9.  To  the  shaft  is  connected  a  recording 
mechanism  of  some  sort,  the  simplest 
being  merely  dials  which  show  the 
velocity  of  the  air  traveling  past  the 
instrument,  by  the  reading  of  which 
against  a  stop-watch,  the  speed  per 
unit  of  time  may  be  obtained.  Since 
the  instrument  works  against  the 
friction  of  moving  parts,  its  readings 
are  subject  to  serious  variation,  and 
even  with  frequent  calibration,  it  is 
not  to  be  relied  upon  where  results 
are  required  accurate  to  within  20 
per  cent.  Various  tests  of  anemom- 
Fiig.  9.  eters  by  comparison  to  the  absolute 


PITOT    TUBE 


33 


reading's  of  a  gas  tank  have  shown  errors  as  high  as  35 
per  cent,  slow,  to  14  per  cent,  fast,  with  the  discharge  from 
pipes  8  inches  to  24  inches  in  diameter.  Hence,  in  general, 
it  is  very  safe  to  say  that  the  anemometer  as  an  instrument 
for  velocity  measurement  in  precise  work  should  be  used 
with  great  care. 

A  second  method  of  velocity  measurement,  and  one 
applying  as  readily  to  liquids  as  to  gases,  is  that  of  using 
the  Pitot  tube  principle.  Whenever,  in  a  liquid  or  gas,  a 
pressure  produces  a  flow,  part  of  this  pressure,  usually 
termed  the  velocity  head,  is  considered  as  transformed  into 
velocity;  while  a  second  part,  usually  called  the  pressure 
head,  acts  to  produce  pressure  in  the  fluid.  If  now,  as  at 
A,  in  Fig.  10,  a  tube  be  inserted  into  a  pipe  carrying'  a 


Fig.   10. 

current  of  air  or  other  moving  fluid,  and  the  end  Of  this 
tube  be  bent  so  the  plane  of  the  opening  is  perpendicular 
to  the  direction  of  the  flow,  a  pressure  in  the  tube  will 
result,  due  to  both  the  velocity  head  and  the  pressure  head; 
and  the  difference  in  levels  in  the  connected  manometer 
tube  will  indicate  this  sum  of  pressures  in  terms  of  inches 
of  water  or  mercury.  If,  however,  a  tube  be  inserted  as  at 
B,  with  the  plane  of  its  opening  parallel  to  the  direction 
of  the  flow,  a  pressure  in  the  tube  will  result,  due  only 
to  the  pressure  head  in  the  moving  fluid;  and  the  difference 
in  levels  in  the  connected  manometer  tube  will  indicate  this 
pressure  only.  Then,  by  subtraction  of  the  two  manom- 
•eter  readings,  the  velocity  head  only  is  obtained,  expressed 
in  inches  of  water  or  mercury,  whichever  the  manometer 
may  contain. 

At  C  is  shown  the  instrument  as  commonly  applied, 
with  both  tubes  together  and  connected  one  to  either  leg 
of  the  manometer  tube  so  that  the  subtraction  is  automatic 


34 


HEATING  AND  VENTILATION 


and  the  difference  in  levels  read  is  caused  by  the  velocity 
only.  Having,  then,  the  head  of  pressure  due  to  velocity, 
to  find  the  actual  velocity  apply  the  formula  v  =  \/2<jh  where 
v  =  velocity  in  feet  per  second,  g  =  acceleration  of  gravity 
in  feet  per  second,  per  second,  and  h  =  the  velocity  head  of 
the  air  in  feet.  If  the  manometer  contains  water,  then, 
at  60  degrees,  the  ratio  between  the  specific  gravity  of  air 

62.37 

and  water  is =  816.4.     See  Tables  12  and  8,  Appendix. 

.0764 

Hence  the  above  formula  may  be  reduced  to  the  more  read- 
ily available  form  of 


Itw 

v  =^|    2    X   32.16   X   816.4   X   ,   or 

12 


v  =  66.2  V 


(8) 


where  hw  =  the  difference  in  height  in  inches  of  the  columns 
of  a  water  manometer,  with  both  legs  connected  as  described, 
and  a  temperature  of  60  degrees.  By  a  similar  method  the 
formula  may  be  reduced  for  a  mercury  or  other  manometer, 
or  for  other  temperatures  than  60  degrees.  (See  Art.  1021, 
Trans.  A.  S.  M.  E.  Vol.  XXV.) 

In  using  the  Pitot  tube  or  the  anemometer,  the  fact 
should  not  be  lost  sight  of  that  the  velocity  varies  from 
a  minimum  at  the  inner  walls  of  the  tube  to  the  maximum 
at  the  center  of  the  tube.  It  seems  that  the  friction  at  the 
inner  walls  throws  the  moving  fluid  into  a  number  of 
concentric  layers,  those  toward  the  center  moving  the  fast- 
est, those  toward  the  inner  wall  of  the  pipe  the  slowest. 
With  a  circular  tube,  the  variation  of  velocities  of  these 
different  layers  may  be  approximately  represented  by  the 
abscissae  of  a  parabola,  Fig.  11,  with  its  axis  on  the  axis  of 
the  circular  pipe.  Weisbach,  on  page  189  of  his  Mechanics  of 


Fig.  11. 


CHIMNEYS  35 

Air  Machinery,  quotes  the  average  speed  at  two-thirds  of  the 
radius  from  the  center,  this  value  being  obtained  by  ex- 
periments. For  conduits  of  other  shapes  the  position  of 
mean  velocity  must  be  determined  experimentally.  This 
variation  of  velocity  from  the  center  of  the  stream  less- 
ening- toward  the  walls  may  possibly  account  for  the  varia- 
tions shown  by  the  anemometers.  It  is  evident  that 
if  such  an  instrument,  with  a  given  diameter  of  vane 
wheel,  be  placed  at  the  center  of  a  pipe  of  large  radius  it 
would  tend  to  register  a  higher  velocity  than  the  average. 
Automatic  recording  meters  may  be  obtained  for  keep- 
ing permanent  records  of  the  flow  of  air  and  steam  through 
pipes  and  ducts.  The  record  from  the  meter  indicates  direct- 
ly the  cubic  feet  of  free  air  or  other  fluid  used  during  each 
hour  of  the  day. 

10.  Amount  of  Air  Required  to  Burn  Carbon: — The  chief 
product  in  the  combustion  of  carbon  with  the  oxygen  of  the 
air  is  CO2.  The  atomic  weight  of  carbon  is  12  and  that 
of  oxygen  is  16,  hence  the  chemical  union  of  the  two  form- 
ing C'O2  is  in  the  proportion  of  carbo.n  12  and  oxygen  32 
or  as  1  :  2.66.  For  each  pound  of  carbon  consumed,  2.66 
pounds  of  oxygen  will  be  needed  and  the  product  will  weigh 
3.66  pounds.  If  pure  air  contains  23  per  cent,  oxygen,  then 
one  pound  of  carbon  will  need  2.66  -r-  .23  =  11.7,  say  12 
pounds  of  air  for  complete  combustion.  One  cubic  foot 
of  air  at  32  degrees  weighs  .0807  pounds,  then  12  -h  .0807  = 
148  cubic  feet  of  air  necessary  to  burn  one  pound  of  car- 
bon if  all  the  oxygen  of  the  air  is  burned.  With  volumes 
proportional  to  the  absolute  temperatures,  this  air  at  70 
degrees  would  be  160  cubic  feet;  at  200  degrees,  200  cubic 
feet;  at  400  degrees,  260  cubic  feet;  and  at  600  degrees,  320 
cubic  feet- 

17.  Probable  Amount  of  Air  Used: — It  seems  reason- 
able to  assume,  however,  that  in  practice  from  two  to  three 
times  as  much  air  goes  through  a  furnace  as  would  be 
needed  for  perfect  combustion.  Taking  this  at  2.5,  then  the 
.cubic  feet  of  air  found  from  the  above  would  be  approxi- 
mately: 32  degrees,  370  cubic  feet;  70  degrees,  400  cubic 
feet;  200  degrees,  500  cubic  feet;  400  degrees,  650  cubic  feet; 
and  600  degrees,  800  cubic  feet. 

IS.  To  Determine  the  Transverse  Area  of  a  Chimney 
for  Any  Given  Height: — Substitute  ho  and  the  assumed 


36  HEATING  AND  VENTILATION 

values  of  tc  and  to  in  formula  7,  Art.  14.  From  this  find 
the  velocity  of  the  chimney  gases,  and  divide  the  total 
volume  of  air  used  in  any  given  time,  Art.  17,  by  the  corre- 
sponding velocity. 

19.  Application    to    the    Chimney    of    a    10-Room    Resi- 
dence:— Given:    total   heat   loss   from   the   building   per   hour, 
10000     B.  •  t.    u.;    coal,     13500    B.    t.     u.    per    pound;     furnace 
efficiency,    60   per   cent.;    temperature   at   bottom   of   chimney, 
200  degrees  F.;  height  of  chimney,   30  feet  above  the  grate; 
average   temperature    of   chimney   gases,    150   degrees.      (The 
greatest    difficulty    is     experienced    when     the     fire    is    first 
started  before  the  chimney  is  warmed  up.     The  temperature 
of  the  stack  gases  at  such  a  time   is  very   low.)      Take  the 
outside  air  temperature,   40  degrees  F.,   and  find   the  size  of 
the  chimney. 

A  heat  loss  of  100000  B.  t.  u.  per  hour  will  require 
100000  -7-  (13500  X  .60)  =  12.4  pounds  of  coal  per  hour  at 
the  grate;  -then  w>ith  a  temperature  of  200  degrees  at  the 
bottom  of  the  chimney,  this  will  need  to  pass  500  X  12.4  = 
6200  cubic  feet  of  air  per  hour.  The  velocity  of  the  chim- 
ney gases,  according  to  formula,  is  20.5  feet  per  second  or 
73800  feet  per  hour.  Assuming  the  real  velocity  to  be 
25  per  cent,  of  this  amount,  we  have  approximately  18450 
feet  per  hour;  then  the  net  sectional  area  is  6200  -i-  18450 
=  .34  square  foot  or  49  square  inches.  To  fit  the  brick 
work  this  would  probably  be  made  8  inches  X  8  inches. 

20.  All   Chimneys  should   have   a    Smooth  Finish   on  the 
Inside: — -Probably   the   best   arrangement   that   can   be    made 
is  to   build  the  chimney  of  hard   burned   brick   around   hard 
burned    tiles    of   suitable    internal    size.      These   tiles    can   be 
had  of  outside   sizes   such  that   they  can   easily  be.  made    to 
work   in  with   the   brick   work.      Table    15,  Appendix,   shows 
chimney    capacities    that   will    be    safe    in    average    practice. 
Flues  should   preferably  be   made   round   in   section,   as   this 
form    presents    less    friction    to    the    gases    than    any    other. 
Flues  should    never   be   built  less    than   ten   inches   in   diam- 
eter,   or   eight   by   ten   inches    rectangular.      The   value   of   a 
flue    depends   very   much   upon   the    volume    of    passage    due 
to   area,  and  velocity   due   to  height.      Velocity  alone   is   no 
proof   of   good   draft   for  there    must  also  be   sufficient  area 
to  carry  the   smoke.     The   top  of  a  chimney  with  reference 


CHIMNEYS  37 

to  Its  position  relative  to  neighboring  structures  Is  a  very 
important  consideration.  If  the  top  is  below  any  nearby 
portion  of  the  building,  eddy  currents  tending  to  enter  the 
top  of  the  flue  may  be  formed  and  seriously  reduce  the  draft. 
Under  such  conditions  a  shifting  cowl,  which  always  turns 
the  outlet  away  from  adverse  currents,  may  be  advisable. 
Good  draft  is  very  essential  to  the  success  of  any  type  of 
heating  system,  and  the  purchaser  of  a  furnace  or  heater 
should  be  required  to  guarantee  sufficient  draft  before  a 
maker  is  expected  to  guarantee  a  stated  rating  of  his 
furnace  or  heater. 


38  HEATING  AND  VENTILATION 


REFERENCES. 

References  on  Ventilation  and  the  Air  Supply 

TECHNICAL  BOOKS. 

Moore,  The  School  House,  p.  24.  Monroe,  Steam  Heat,  d  Vent., 
p.  99.  Carpenter,  Heat.  &  Vent.  Bldgs.,  p.  21.  Hubbard,  Power, 
Heat.  &  Vent.,  p.  408.  Allen,  Notes  on  Heat.  &  Tent.,  p.  91. 
Ency.  Brit.,  Vol.  XXIV,  p.  157,  also  Vol.  XX,  p.  474. 

TECHNICAL  PERIODICALS. 

Engr.  Rev.,  Sanitation  and  Ventilation  in  Boston  School 
Houses,  W.  B.  Snow,  March  1908,  p.  15,  Subw  ».y  Ventilation, 
J.  B.  Holbrook,  Jan.  1905,  p.  18.  Ventilation  of  School  Rooms, 
Nov.  1905,  p.  6.  Heat.  &  Vent.  Magazine.  A  Scotchman's  Notes  on 
Ventilation,  Alex.  Mackenzie,  May  1906,  p.  15.  Air  Analysis  as 
an  Aid  to  the  Ventilating  Engineer,  J.  R.  Preston,  Oct.  1906, 
p.  11.  Domestic  Engineering.  Ventilation  in  its  Relation  to  Health 
W.  G.  Snow,  Vol.  52,  No.  4,  July  23,  1910,  p.  102;  Vol.  52,  No. 
6,  Aug.  6,  1910,  p.  154.  Ventilation  of  Isolated  Offices,  C.  L. 
Hubbard,  Vol.  45,  No.  10,  Dec.  5,  1908,  p.  274.  Humidity, 
Its  Necessity  and  Benefits,  W.  W.  Brand,  July  1910. 
The  Permanent  Place  of  the  Air  Washer  in  Heating 
and  Ventilating-  Work,  Feb.  1910.  Trans.  A.  8.  H 
&  V.  E.  The  Necessity  of  Moisture  in  Heated  Houses,  R.  C. 
Carpenter,  Vol.  X,  p.  129.  Need  of  Ventilation  in  Heated 
Buildings,  Vol.  X,  p.  183.  Changing  the  Air  in  a  Building, 
Vol.  X,  p.  285.  Effect  of  Humidity  on  Heating  Systems,  Vol. 
IX,  p.  323.  Necessity  of  Ventilation,  H.  Eisert,  Vol.  V,  p.  57. 
The  Engineering  Magazine.  Humidifiers, — Their  Principles  and 
Useful  Applications,  S.  H.  Bunnell,  June  1910.  The  Heating, 
Ventilating  and  Air  Conditions  of  Factories,  P.  R.  Moses, 
Aug.  and  Sept.  1910.  Engineering  Record.  Ventilation  of  Three 
Basement  Floors  of  the  Marshall  Field  Retail  Store,  Chica- 
go, Jan.  23,  1909.  Ventilation  of  a  Newspaper  Photo-En- 
graving Plant,  June  26,  1909.  Ventilation  of  the  First 
Church  of  Christ,  Scientist,  Boston,  Sept.  19,  1908.  The  Ven- 
tilation of  a  Weave  Shed,  Aug.  8,  1908.  Ventilati9n  of  the  Bat- 
tery Tunnels  of  the  New  York  Subway  Extension  to  Brook- 
lyn, Oct.  5,  1907.  Railway  Tunnel  Ventilation,  Feb.  20,  1904. 
Railway  Age  Gazette.  Detroit  Return  Trap  System,  July  23, 
1909,  p.  175.  Washington  Union  Station  Ventilation,  June 

12,  1908,  p.  84.     Heating  and  Ventilating  the  Storage  Battery 
Stations    on   the   New   York   Central   &   Hudson   River,   April 

13,  1908,  p.  489.     Ventilation  and  Heating  of  Engine  Round- 
houses as  Adopted  by  the  New  York  Central  Lines,  June  18, 
1909,  p.  1335.     The  Metal  Worker.     A  Remarkable  Theatre  Ven- 
tilation Plant,  Jan.   15,   1910,   p.    63.     An  Interesting  Factory 
Ventilation  Plant,  Jan.  15,  1910,  p.  90.  Ventilation  of  Factories, 
Auditoriums,  Stores   and  Schools  in  Chicago,  May   7,   1910,   p. 
634.     Ventilation  in 'Relation  to  Health,  Wm.  G.  ~Snow,   June 
25,  1910,  p.  866;  July  30,  1910,  p.  142.     Heating  and  Ventilat- 
ing  Plant   Complying   with    Factory   Law,    July    10,    1909,    p. 
41.      Heating    from    a   Physician's   Standpoint,    May    14,    1910, 
p.     658.      Ventilating    a    Restaurant,    Sept.     25,     1909,    p.     39. 
Cassier's  Magazine.     The  Purification  of  Air,  Oct.  1910. 


CHAPTER  III. 


HEAT   LOSSES   FROM   BUILDINGS. 


21.       Loss    of    Heat    by     Conduction    and    Radiation: — In 

planning  the  heating  system  for  any  building,  the  first  and 
probably  the  most  important  part  of  the  work  is  to  esti- 
mate the  total  heat  loss  per  hour  from  the  building.  Un- 
fortunately this  is  the  part  which  is  the  least  open  to 
satisfactory  calculations  and  we  find  little  valuable  theo- 
retical data  upon  the  subect. 

Heat  is  lost  from  a  building  in  two  ways,  by  radiation 
and  by  convection,  i.  e.,  that  transferred  through  walls,  win- 
dows and  other  exposed  surfaces  by  conduction  and  lost 
by  radiation;  >and  that  carried  off  by  the  movement  of  the 
air  as  it  passes  out  through  the  openings  in  the  building 
to  the  outside  air.  The  radiation  loss  is  usually  of  greater 
importance,  but  the  convection  loss  is  of  much  more  im- 
portance than  is  generally  considered.  In  the  average 
building  both  of  these  values  are  difficult  to  determine. 

Radiation  losses  are  considered  under  various  heads, 
such  as  glass,  wall,  floor,  ceiling  and  door  losses.  Concern- 
ing the  conduction  of  heat  through  these  various  materials, 
the  available  data  have  been  obtained  by  experimentation 
and  do  not  agree  very  closely.  Peclet  in  France,  and  Gras- 
hof,  Rietschel,  Klinger  and  Rechnagel  in  Germany,  each 
carried  on  experimental  research  to  determine  the  heat 
transmission  through  various  materials  and  structures. 
These  published  data  form  the  basis  for  a  large  part  of  the 
heat  loss  calculations  of  the  present  time.  Much  valuable 
material  can  be  found  in  the  more  recent  writings  of 
Hood,  Wolff,  Box,  Carpenter,  Kinealy,  Allen,  Hogan,  Hub- 
bard  and  others,  but  many  of  the  values  quoted  are  only 
rough  approximations  at  best.  The  reason  for  so  much 
uncertainty  in  this  part  of  the  work  is  found  in  the  fact 
that  there  are  such  great  differences  in  methods  of  build- 
ing construction.  Conductivity  tests  for  the  various  ma- 
terials have  been  satisfactorily  made,  but  when  these  same 
materials  have  been  put  into  a  building  wall  the  quality 
of  the  workmanship  often  permits  more  heat  loss  by  con- 


40  HEATING  AND  VENTILATION 

vection  than  would  be  transmitted  through  the  materials 
themselves.  The  values  quoted  for  brick  walls  and  glass 
agree  fairly  well.  The  greatest  difficulty  is  found  in  the 
balloon-framed  bui'lding  with  its  studded  walls,  where  the 
dead  air  space  in  a  well  constructed  wall  may  be  a  good 
non-<conductor,  or  where,  on  the  other  hand,  the  same  space 
in  a  poorly  constructed  wall  may  become  a  circulating  air 
space  to  cool  the  walls  by  the  movement  of  the  air. 

Table  IV  has  been  compiled  from  a  number  of  the 
best  references  as  stated  above,  and  represents  a  fair  aver- 
age of  all  of  them.  The  value  K  (rate  of  transmission),  in 
some  of  the  references,  varied  for  the  same  material,  being 
somewhat  greater  for  small  temperature  differences  than 
where  the  temperatures  differed  widely.  In  general,  the 
transfer  of  heat  -through  any  substance  is  about  propor- 
tional to  the  difference  of  the  temperature  between  the  two 
sides  of  the  'Substance.  This  was  noticeably  'true  for  most 
of  the  quotations. 

TABLE   IV. 

Conductivities  of  Building  Materials. 
K  =  B.  t.  u.  transmitted  per  sq.  ft.  per  hour  per  degree  dif. 

Materials.  K. 

Brick  wall,     8"    4 

Brick  wall,   12" 31 

Brick  wall,  16"    26 

Brick  wall,  20" 23 

Brick  wall,  24"    21 

Brick  wall,  28"    19 

Brick  wall,  32"    17 

Brick  wall,  furred,  use  .7  times  non-furred  in  each  case. 
Stone  wall,  use  1.5  times  brick  wall  in  each  case. 

Windows,  single  glass i.o 

Windows,  double  glass 6 

Skylight,  single  glass   • 1.1 

Skylight,  double  glass    7 

Wooden  door,  1" i 4 

Wooden   door  2" 36 

Solid  plaster  partition,   2" 6 

Solid  plaster  partition,   3" .5 

Ordinary  stud  partition,  lath  and  plaster  on  one  side 6 


HEAT    LOSSES    FROM    BUILDINGS  41 

Ordinary  stud  partition,  Lath  and  plaster  on  two  sides..      .34 

Concrete  floor  on  brick  arch 2 

Fireproof  construction  as  flooring 1 

Fireproof  construction  as  ceiling 14 

Single  wood  floor  on  brick  arch 15 

Double  wood  floor,   plaster  beneath 10 

Wooden  beams  planked  over,  as  flooring 17 

Wooden  beams  planked  over,  as  ceiling 35 

Walls  of  the  average   wooden  dwelling 25  to  .30 

Lath  and  plaster  ceiling,  no  floor  above 62 

Lath  and  plaster  ceiling,  floor  above 25 

Steel  ceiling,  with  floor  above 35 

Single   %"  floor,   no  plaster  beneath 45 

Single  %'"  floor,  plaster  beneath 26 


Occasionally  it  is  convenient  to  reduce  all  radiating 
surfaces  to  equivalent  wall  surface  and  take  account  of  the 
heat  losses  as  a  part  of  the  wall. 

The  following  equivalents  for  doors,  floors  and  ceilings 
have  been  found  to  give  good  results: 

Doors  not  protected  by  storm  doors  or  vestibule  =  200%  of 
equal  wall  area. 

Floor  over  unheated  space.  Air  circulation  =  same  as  wall. 
Floor  over  unheated  space.  Still  air  =  40%  of  equal  wall  area. 
Ceiling  below  unheated  space.  Air  circulation  =  125%  of 
equal  wall  area. 

Ceiling  below  unheated  space.  Still  air  =  50%  of  equal  wall 
area. 

In  all  references  from  French  and  German  authorities, 
one  is  impressed  by  the  extreme  care  and  exactness  with 
which  every  detail  is  worked  out,  even  to  those  minor  parts 
usually  considered  in  this  country  of  no  special  moment. 

Table  IV  has  been  reduced  to  chart  form,  Fig.  12,  where 
the  table  values  agree  with  — 10°  outside  temperature  and  0 
wind  velocity.  The  application  of  this  chart  is  as  follows: 
Assume  the  outside  temperature  — 10°,  still  air,  inside  tem- 
perature 70°,  south  exposure.  What  is  the  heat  loss  from 
a  square  foot  of  12  inch  brick  wall,  also  from  a  square  foot 
of  single  glass  window?  Beginning  at  the  right  of  the 
chart  at  — 10°  outside  temperature  trace  to  the  left  to  the 
0  wind  velocity,  then  up  the  ordinate  to  the  12  inch  wall 


42 


HEATING  AND  VENTILATION 


(interpolate  between  8  and  16),  then  to  the  left  to  the  line 
indicating  70°  inside  temperature,  then  down  to  the  south 
exposure,  then  to  the  left  showing  25  B.  t.  u.  transmitted 


Fig.   12. 


per  hour.  For  the  glass,  trace  from  —10°  to  the  0  wind 
velocity,  then  up  to  the  single  window,  then  to  the  left  to 
the  inside  temperature,  70°,  then  down  to  south  exposure, 


ESTIMATION   OF    HEAT    LOSS  43 

then  to  the  left  showing  80  B.  t.  u.  per  square  foot  per  hour. 
Checking  this  with  the  table  for  a  12  inch  brick  wall  we 
have  .31  X  80  —  24.8  B.  t.  u.  For  glass  1  X  80  =  80.  The 
values  given  in  the  table  must  be  increased  for  west,  north 
and  east  exposures.  The  effect  of  the  wind  velocity  upon 
the  heat  loss  is  very  marked.  Locations  subjected  to  high 
winds  should  have  extra  allowance  made.  For  example, 
take  the  12  inch  brick  wall  just  mentioned.  Assume  the 
wind  to  be  30  miles  an  hour.  By  the  same  process  as  before 
we  find  for  a  south  exposure,  36  B.  t.  u.  loss  as  compared  to 
25  with  0  wind  velocity. 

22.  Loss   of  Heat  by  Air   Leakage: — The   exact   amount 
of   air    leaving    a   building   by   leakage    is    impossible   to   de- 
termine.     Many    experiments    have    been   -carried    on    in    the 
last  few  years  to  determine  the  amount  of  leakage  around 
windows   and   doors.     These  in  the   specific   cases   have   been 
successful,    but  no  actual   values   can   be   quoted  for  general 
use.      Again,    a    considerable    amount    of   air    passes    through 
the  walls,  thus  rendering  the  case  more  complicated.     In  all 
the    experiments,    however,    it    has    been    found    that    these 
losses  have  been  much  greater  than  was  supposed.     In  rooms 
not    heavily    exposed,    or    in    touch    with    heavy    winds,    two 
changes    per    hour   may    be    safely    allowed    for    all    leakage 
.losses. 

23.  Exposure     Losses     and     Other     Losses: — Radiation 
losses  are  much  greater  on  the  exposed  or  windward  side  of 
the   building.     Moving  air   passing   over  the   surface   of   any 
radiating  material  will  wipe  the  heat  off  faster  than  would 
be  true  of   still  air.     The   north,  north-west  and  the  north- 
east in  most  sections  of  the  country  get   the   highest  winds 
and    have    the    least    benefit    of    the    sun    and    are    therefore 
counted    the    cold    portions    of   the    building.      In    figuring   a 
building   it   is   customary   to   figure   each   room   as   though   it 
were  a  south  room,  which   is  assumed  to   need   no  additions 
for    exposure,    and    then    add    a    certain    percentage    of    this 
loss  for  exposure  to  fit  the  location  of  the  room.     The  exact 
amount  to  add  in  each  case  is  largely  a  matter  of  the  judg- 
ment of  the   designer,  who,   of  course,   is   supposed   to   know 
the    direction    of    the    heavy   winds    and   the    protection    that 
is    afforded    by    surrounding    buildings.      A    wide    variety    of 
values   covering  the  American  practice  might  be  quoted  for 
this,   but  the   following  will  give  satisfactory   results: 


44  '     HEATING  AND  VENTILATION 

TABLE  V. 

North,    north-east    and    north-west    rooms    heavily    exposed, 

10-20  per  cent. 
East  or  west  rooms   moderately   exposed  ....   5-10  per  cent. 

Rooms  heated  only  periodically 20-40  per  cent. 

The    German   practice   is   somewhat   more   extreme    than 
ours  in  this  part  of  the  work: 
North,  north-east  and  north-west  rooms  heavily  exposed 

15-25  per  cent. 

East  and  west  rooms   10-15  per  cent. 

Surfaces   exposed  to  heavy  winds 10-20  per  cent. 

Heat  interrupted  daily  but  rooms  kept  closed  10  per  cent. 
Heat  interrupted  daily  but  rooms  kept  open  30  per  cent. 

Heat  off  for  long  periods 50  per  cent. 

Rooms  12  to  14%  feet  from  floor  to  ceiling  ..  3  per  cent. 
Rooms  14%  to  18  feet  from  floor  to  ceiling  ...  6  per  cent. 
Rooms  18  feet  and  above  from  floor  to  ceiling  10  per  cent. 


24.  Loss  of  Heat  by  Ventilation: — A  certain  amount   of 
fresh   air  leaks  into  every  building   and   displaces   an   equal 
amount  of  warm  air,    but   this  amount  of  fresh  leakage  air 
is    not    considered    sufficient    for    good    ventilation.      When, 
warm  air  is   displaced   either  by  leakage   or  by   ventilation, 
it  is  exhausted  to  the  outside  air  and  as  it  leaves  the  room 
carries  a  certain  amount  of  heat  with  it.     This  is  a  direct 
loss  and  should  be  taken  into  account. 

Since  the  loss  by  leakage  is  practically  the  same  for 
all  systems  of  heating,  it  is  accounted  for  in  the  ordinary 
heat  loss  formula,  but  losses  by  ventilating  systems  must 
be  considered  in  excess  of  this  amount.  Let  Q'  =  cubic  feet 
of  fresh  air  supplied  per  hour,  V  —  to  =  drop  in  temperature 
from  the  inside  to  the  outside  air;  then  the  heat  lost  by  ex- 
hausting the  air,  Art.  27,  is 

Q'  (*'  —  to) 
H,  =  — (9) 

55 

25.  Two  General  Methods  of  Estimating  the  Heat  Lo«»  H 
from    a    Building    are    In    Common    Use: — First,    estimate    all 
radiation   losses   and    add   to    their   sum   a    certain   per   cent. 


ESTIMATION   OF    HEAT    LOSS  45 

of  itself  to  allow  for  leakage  by  convection;  second,  esti- 
mate all  radiation  losses  and  add  to  their  sum  a  certain 
amount  which  depends  upon  the  volume  of  the  room.  The 
first  is  by  Equivalent  Radiating  Surfaces  only  and  the  second  is 
by  Equivalent  Radiating  Surfaces  and  Volume  combined. 

26.  Method  No.  1: — Figuring  by  Equivalent  Radiating 
Surface. — Let  H  --  B.  t.  u.  heat  loss  from  room  per  hour; 
O  —  exposed  glass  in  square  feet;  W  =  exposed  wall  minus 
glass,  plus  exposed  doors  reduced  to  equivalent  wall  surface 
in  square  feet;  F  =  floor  or  ceiling  separating  warm  room 
from  unheated  space;  tx  =  difference  between  room  temper- 
ature and  outside  temperature;  ty  =  difference  between 
room  temperature  and  temperature  of  the  unheated  space; 
K,  K'  and  K"  —  coefficients  of  heat  transmission;  a  =  per- 
centage allowed  for  exposure  and  6  =  percentage  allowed 
for  loss  by  leakage,  varying  in  per  cent,  of  other  losses 
from  10  in  the  average  house  to  30  in  the  house  of  poor 
construction. 

From  the   above,   we   have 

H  =  (KGt*  +  K'Wt*  +  K"Ftv)    (1  +  a  +  6)  (10) 

(APPLICATION. — Assume  the  sitting  room,  Fig.  15,  to  have 
a  total  exposed  wall  surface,  W,  exclusive  of  glass,  242 
square  feet;  total  exposed  glass,  O,  38  square  feet;  and 
floor,  F,  195  square  feet.  Assume  that  all  the  rooms  are 
heated  to  70  degrees  with  an  outside  temperature  of  zero 
degrees  and  that  all  workmanship  is  fair.  Assume  also  the 
floor  to  be  of  the  ordinary  thickness  and  not  ceiled  below,  with 
a  temperature  below  the  floor  of  this  room  of  32  degrees; 
and  that  two  people  are  using  the  room.  Under  such  con- 
ditions what  is  the  heat  loss  from  the  room?  Since  this 
is  a  south  room  there  is  no  exposure  losis  and  a  =  0.  Then 
assuming  o  =  .20  we  have 

H  =  (1  X  38  X  70  +  .3  X  242  X  70  +  .45  X  195X  38)  (1  +  .20) 
=  13270  B.  t.  u. 

Good  judgment  will  be  necessary  in  selecting  the  proper 
outside  temperature  for  the  calculation.  The  value  of  this 
outside  temperature  varies  'among  men  in  the  same  locality 
as  much  as  20  degrees.  In  the  above  application  if  to  =  — 
20°  and  the  temperature  of  the  unheated  space  below  the 
floor  remains  at  32  degrees,  formula  (10)  becomes  H  =  15946 
B.  t.  u.  See  discussion  of  this  point  under  Art.  60. 


46  HEATING  AND  VENTILATION 

27.  Method    Xo.    2: — Figuring    by    Equivalent    Radiating 
Surface  and  Volume. — The  general   formula   for  this   is 

H  =  (KQt,  +  K'Wt*  +  K"Fty  +  oc  nCtx)    (1  +  o)  (11) 

where  H,  K,  O,  tx,  ty,  W,  F  and  a  are  as  given  above;  C  =  cubic 
volume  of  the  room;  n  =  number  of  times  the  air  is  sup- 
posed to  change  in  the  room  by  leakage  and  convection  per 

hour,  recommended,  1  to  2;    K  =  ~  and  is  usually  taken  .02 

55 
for  convenience  of   calculation.     This   constant  refers  to  the 

heat  carried  away  by  the  air.  The  specific  heat  of  the  air 
at  32  degrees  is  .238;  then  the  number  of  pounds  of  air 
heated  from  32  to  33  decrees  by  1  B.  t.  u.  is  1  -T-  .238  =  4.2. 
Now  if  the  weight  of  a  cubic  foot  of  air  at  32  degrees  is  .0807 
pounds,  we  would  have  4.2  -~  .0807  =  52  cubic  feet  of  air 
heated  from  32  to  33  degrees  by  1  B.  t.  u.  However,  most 
of  the  heating  is  not  done  at  from  32  to  33  degrees  but 
from  32  to  70  degrees,  in  which  case,  the  volume  of  air 
heated  from  69  to  70  degrees  by  1  B.  t.  u.  is  52  X  530  ^ 
492  =  56  cubic  feet.  See  absolute  temperature,  Art.  4.  It 
is  evident  that  some  approximation  must  here  be  made.  No 
exact  value  can  be  taken  because  of  the  great  range  of 
temperature  change  of  the  air,  but  55  is  commonly  used 
as  the  best  average.  The  difficulty  of  'handling  formula 

with  the  constant   —  has  led  to  the  simple  form  .02.      (See 

5o 
last  column  Table  12,  Appendix.) 

APPLICATION. — With  the  same  room  as  used  in  Application 
1,  we  have,  if  a  =  0, 

'  H  =  (1  X  38  X  70  +  .3  X    242   X   70  +  .45   X   195   X   38  + 
.02  X  1  X  1950  X  70)   (1  +  0)  =  13806  B.  t.  u. 

28.  Method   No.   3: — Professor     Carpenter     reviews     the 
work    of    the    various    authors    and    quotes    the    following 
formula,   which  is  the  same  as  that  given  in  Method  No.   2 
In   a    more    simplified    form,    with    the    terms    the    same    as 
before: 

H  =  ((?  +   .25  W  +  .02  nC)   t,  (12) 

In  his  opinion  ithe  very  elaborate  methods  sometimes  used 
are  unnecessary.  K  may  be  assumed  .25  for  any  ordinary 
wall  surface,  brick  or  frame,  and  the  ceilings  adjoining  an 
attic  or  the  floors  above  a  cellar  of  the  average  house  need 
not  be  considered.  Floors  above  an  unexcavated  space 
where  no  heat  is  obtained  from  the  furnace  and  where  there 


ESTIMATION   OF   HEAT   LOSS  47 

is  more  or  less  circulation  of  air  should  no  doubt  have 
some  allowance.  This  would  probably  be  the  same  as  given 
in  Art.  21.  The  values  of  n  are  quoted  by  the  same  author- 
ity as  follows: 

Values  of  n. 


Residence  heating,   halls,   3;   sitting  room  and  rooms   on  the 
first  floor,  2;  sleeping  rooms  and  rooms  on  second  floor,  1. 
Stores,  first  floor,  2  to  3;  second  floor,  iy2  to  2. 
Offices,  first  floor,  2  to  2y2;  second  floor,  1%  to  2. 
Churches  and  public  assembly  rooms,   %  to  2. 
Large  rooms   with   small   exposure,  %  to   1. 


APPLICATION. — Assuming   the   same    room   as   before, 
//  =  [38  +  .25  (242  +  .4  X  195)  +   .02  X  2  X  1950]  70  =  13720. 

29.  Combined  Heat  Loss  H'  =  (H  +  Ev) :— In  buildings 
where  ventilation  is  provided,  the  total  heat  loss  is  that  lost 
by  radiation,  //,  +  that  lost  by  ventilation,  Hv,  Csee  also  Art. 
36).    Letting   Qv    —   cubic   feet    of    air    needed    per    hour   for 

ventilation,  we  have 

Q»  U 

H'  =  H   H (13) 

55 

Rule. — To  find  the  total  heat  loss  from  any  building,  add  to 
the  heat  loss  calculated  by  formula,  the  amount  found  by  multiply- 
ing the  number  of  cubic  feet  of  ventilating  air  exhausted  from  the 
building  per  hour  by  one-fifty-fiffh  of  the  difference  between  the  in- 
side and  outside  temperatures. 

30.  Temperatures    to    be    Considered: — The    temperature 
maintained  in  heated  rooms    in  this   country   is   70   degrees. 
Outside   temperatures  used  in  figuring  heat  losses  are  gen- 
erally taken,   southern  part,  +  10  degrees;   northern  part  — 
20  degrees;  ordinary  value,  0  degrees.      (See  Art.  60.) 

The  German  Government  requires  estimates  on  the  fol- 
lowing temperatures,  as  quoted  in  "Formulas  and  Tables 
for  Heating,"  by  Prof.  J.  H.  Kinealy. 


48  HEATING  AND  VENTILATION 

TABLE   VI.— Values   of  *'. 


The    temperatures    of    heated    rooms    are    generally    as- 
sumed by  the  German  Engineers  to  be  as  follows: 

Rooms  in  which  the  occupants  are  for  the  most  part  at  rest: 
Living  rooms,   business   rooms,   court   houses,   offices, 

schools      68 

Lecture  halls  and  auditoriums    61  to   64 

Rooms  used  only  as  sleeping  rooms 54  to  59 

Bath  rooms   in  dwellings 68  to   72 

Sick   rooms     72 

Rooms    in   which    the    occupants    are    undergoing    bodily    ex- 
ertion: 

Workshops,  gymnasiums,  fencing  halls,  etc.,  in  which 

the  exertion  is  vigorous  50  to  59 

Workshops  in  which  the  exertion  is  not  so  vig- 
orous   61  to  64 

Rooms  used  as  passage  rooms  or  occupied  by  people  in 

street   dress: 

Entrance    halls,    passages,    corridors,    vestibules   54   to  59 

Churches   50  to  54 

Miscellaneous: 

Prisons  for  the  confinement   ot  prisoners  during 
the  day     64 

Prisons  for  the  confinement  of  prisoners  during 
the  night     50 

Hot  .houses .77 

Cooling  houses    59 

Bath  houses: 

Swimming    halls     68 

Treatment  rooms,  massage  rooms 77 


•Steam  bath 113 

Warm  air  bath     122 

Hot  air  bath  140 


ESTIMATION    OF    HEAT   LOSS  49 

TABLE   VII. 
Values   of  to  When  Applied   to   a  Room. 

The  temperatures  of  rooms  not  heated  are  quoted  aa 
follows,  with  the  outside  air  at  4  degrees  below  zero: 

'Cellars  and  rooms  kept  closed 32 

Rooms  often  in  communication  with  the  outside  air, 
such  as  passages,  entrance  halls,  vestibules,  etc.  23 
Attic    rooms    immediately    beneath    metal    or    slate 

roof     14 

Attic    rooms    immediately    beneath    tile,    cement,    or 
tar  and  gravel   roof    23 

31.  Heat  given  off  from  Lights  and  from  Persons 
Within  the  Room: — As  a  credit  to  the  heating  system,  some 
heating  engineers  take  account  of  the  heat  radiated  from 
the  lights  and  the  persons  within  the  room.  The  following 
table  by  Rubner  is  quoted  by  Prof.  Kinealy: 

TABLE  VIII. 

Gas,  ordinary  split  burner,  B.  t.  u.  per  candle  power  hr.    300 
Gas,  Argand  "          "     200 

Gas,   Auer  "          "  "  "         "       31 

Petroleum  "         "  "  "          *   "         "     160 

Electric,  incandescent  "  "  "  "         "       14 

Electric,  arc  "  "  "  "  4.3 

According  to  Pettenkofer,  the  mean  amount  of  heat 
given  off  per  person  per  hour  is  400  heat  units  for  adults 
and  200  for  children. 


50  HEATING  AND  VENTILATION 


REFERENCES. 

References  on  Heat  Losses  and  Radiation. 

TECHNICAL  BOOKS. 

Snow,  Principles  of  Heat.,  p.  54.  Carpenter,  Heating  and 
Ventilating  Bldgs.,  p.  64.  Hubbard,  Poicer,  Heat,  and  Vent.,  p.  417. 
Allen,  Notes  on  Heat,  and  Vent.,  p.  13. 

TECHNICAL  PERIODICALS. 

Engineering  Review.  Air  Leakage  Around  "Windows;  Its 
Prevention  and  Effects  on  Radiation,  Harold  McGeorge,  Feb. 
1910,  p.  64.  The  Heating  and  Ventilating  Magazine.  Austrian  Co- 
efficients for  the  Transmission  of  Heat  through  Building  Ma- 
terials, W.  W.  Macoii,  Feb.  1908,  p.  36.  Air  Leakage  through 
Windows  and  its  Effect  Upon  the  Amount  of  Radiation,  B. 
S.  Harrison,  Nov.  1907,  p.  18.  Air  Leakage  Around  Windows 
and  its  Prevention,  H.  W.  Whitten,  Dec.  1907,  p.  20.  Deriva- 
tion of  Constants  for  Building  Losses,  R.  C.  Carpenter, 
March  1907,  p.  34.  Methods  of  Estimating  Heat  Losses  from 
Buildings,  C.  L.  Hubbard,  Sept.  1907,  p.  1.  Trans.  A.  8.  H.  & 
V.  E.  Heat  Losses  and  Heat  Transmission,  Walter  Jones, 
Vol.  XII,  p.  233.  Loss  of  Heat  through  Walls  of  Buildings, 
R.  C.  Carpenter,  Vol.  VIII,  p.  96.  Engineering  Record  .  An  In- 
vestigation of  the  Heat  Losses  in  an  Electric  Power  Station, 
Jan.  16,  1909,  p.  77.  Derivations  of  Constants  for  Bldg. 
Losses,  R.  C.  Carpenter,  Feb.  23,  1907.  p.  214.  The  Metal  Worker. 
Humidity  of  Air  and  Its  Determination,  with  Chart,  Aug.  21, 
1909,  p.  56.  Heating  Water  by  Steam,  Sept.  18,  1909,  p.  53. 
Coal  Consumption  in  Two  English  Hot  Water  Heating 
Plants,  Sept.  19,  1908,  p.  47.  School  House  Warming  and 
Ventilation,  Serial,  Jan.  6,  1906,  p.  58.  Power.  Heat  Trans- 
mission through  Corrugated  Iron,  A.  H.  Blackburn,  Oct.  29, 
1912.  Coal  Required  to  Heat  Modern  City  Building,  E.  F. 
Tweedy,  Jan.  16,  1912. 


CHAPTER  IV. 


FURNACE   HEATING   AND    VENTILATING. 


PRINCIPLES   OF  DESIGN. 

32.     Furnace   Systems   Compared  with   Other  Systems: — 

The  plan  of  heating  residences  and  other  small  buildings 
by  furnace  heat,  in  which  the  air  serves  as  a  heat  carrier,  is 
a  very  common  one  in  this  country.  Some  of  the  points  in 
favor  of  the  furnace  system  are:  low  cost  of  installation, 
heating  combined  with  ventilation,  and  the  rapidity  with 
which  the  system  responds  to  light  service  or  to  sudden 
changes  of  outdoor  temperatures.  Compared  with  that  of 
other  heating  systems,  the  furnace  system  can  be  installed 
for  one-third  to  one-half  the  cost.  In  addition  to  this,  the 
fact  that  ventilation  is  so  easily  obtained,  and  the  fact  that 
a  small  fire  on  a  mild  day  may  be  sufficient  to  remove  the 
chill  from  all  the  rooms,  give  this  method  of  heating  many 
advocates.  The  objections  to  the  system  are:  cost  of  operation 
when  outside  air  is  circulated,  difficulty  of  heating  the 
windward  side  of  the  house,  and  the  contamination  of  the 
air  supply  by  the  fuel  gases  leaking  through  the  joints  in 
the  furnace.  In  a  good  system  well  installed,  the  only 
objection  to  be  seriously  considered  is  the  difficulty  of  heat- 
ing that  part  of  the  house  subjected  to  the  pressure  of  the 
heavy  wind.  The  natural  draft  from  a  warm  air  furnace 
is  not  very  strong  at  best  and  any  differential  pressure 
in  the  various  rooms  will  tend  to  force  the  air  toward  the 
direction  of  least  resistance.  The  cost  of  operating  can  be 
controlled  to  the  satisfaction  of  the  owner,  consistent  to  his 
ideas  of  the  quality  of  the  ventilation  needed.  Arrange- 
ments may  be  made  to  carry  the  warm  air  from  the  room 
back  again  to  the  furnace  to  be  reheated,  in  which  case, 
if  the  fresh  air  be  cut  off  entirely,  the  cost  of  heating  is 
about  the  same  as  that  of  any  system  of  direct  radiation 
having  no  provision  for  ventilation.  Any  amount  of  fresh 
air,  however,  may  \  °  taken  from  the  outside  for  the  pur- 
pose of  ventilation,  thus  requiring  the  same  amount  of  air 


52 


HEATING  AND  VENTILATION 


to   be    exhausted   at   the    room  .temperature   and    causing   an 
increased  cost   of   operation,  as  discussed   in  Art.    36. 

33.  Essentials  of  the  Furnace  System: — Fundamentally, 
this  installation  must  contain:  first,  a  furnace  upon  proper 
settings;  second,  a  carefully  designed  and  constructed  sys- 
tem of  fresh  air  supply  and  return  ducts;  and  third,  the 
warm  air  distributing  leaders,  stacks  and  registers.  Fig. 
13  shows,  in  elevation,  a  common  arrangement  of  these 
essentials,  and  gives,  also,  the  air  circulation  by  arrovv 


Fig.   13. 

directions.  The  installation  shown  is  rendered  flexible  In 
operation  by  the  basement  dampers,  proper  adjustment  of 
which  will  allow  fresh  air  to  be  taken  from  either  side 


FURNACE   HEATING  53 

of  the  house  or  furnished  to  the  pit  under  the  furnace  by  the 
duct  from  the  first  floor  rooms.  This  return  register  is 
usually  placed  in  the  hall,  under  the  stairway,  or  in  some 
room  which  is  generally  in  open  connection  with  the  other 
rooms  on  the  first  floor,  as  a  large  living  room. 

34.  Points  to  fo,e   Calculated  in  a  Furnace  Design: — Be- 
sides   the    calculated    heat   loss,    H,    which    of   course    would 
probably    be    the    same    for    all    methods    of    heating,    other 
points   in  furnace  design  would  be  taken  up   in  the  follow- 
ing   order:    first,    find    the    cubic    feet    of    air    needed    as    a 
heat  carrier  and  determine  if  this  amount  of  air  is  sufficient 
for  ventilation;   then   calculate   the   areas   of  the   following: 
net    heat    register,     gross    heat     register,    heat     stack,     net 
vent  register,   gross  vent  register,  vent  stack,  leader  pipes, 
fresh  air  duct  and  total  grate  area.     From  the  total  grate 
area  the  furnace  may  be   selected. 

35.  Air  Circulation  in  Furnace  Heating:: — The  use  of  air 

in  furnace  heating  may  be  considered  from  two  standpoints, 
each  very  distinct  in  itself.  First,  air  as  a  heat  carrier; 
second,  air  as  a  health  preserver.  The  first  may  or  may  not 
provide  fresh  air;  it  merely  provides  enough  air  to  carry 
the  required  amount  of  heat  from  the  furnace  to  the  rooms, 
1.  e.,  to  take  the  place  of  the  heat  lost  by  radiation  plus 
the  small  amount  that  is  carried  away  by  the  natural  in- 
terchange of  air  from  within  to  without  the  building,  as 
would  be  true  in  any  residence  that  is  not  especially  planned 
to  provide  ventilation.  With  certain  allowable  temperatures 
at  the  various  parts  of  the  system,  this  volume  of  air  may 
be  easily  calculated.  One  point  here  should  be  remembered: 
when  the  cubic  feet  of  air  per  hour  as  a  heat  carrier  is 
found  at  the  register,  this  volume  remains  the  same,  no 
matter  if  it  enters  the  furnace  through  a  duct  from  within 
or  without  the  building.  So  this  plan  may  be  both  a  heat 
carrier  and  a  ventilator  if  desired,  subject  only  to  the 
amount  of  air  required.  The  seco  plan  requires  that 
enough  air  be  sent  to  the  rooms  to  provide  ventilation.  If 
this  amount  is  less  than  that  needed  as  a  heat  carrier,  all 
well  and  good,  the  first  amount  will  be  used;  but  if  it 
should  be  greater,  then  the  first  amount  will  need  to  be 
increased  arbitrarily  to  agree.  This  increased  volume  will 
then  be  used  instead  of  that  calculated  as  a  heat  carrier 


5  4  HEATING  AND  VENTILATION 

only.  As  previously  stated,  the  cubic  feet  of  air  per  hour 
as  a  ventilator  may  be  taken  as  1800  N,  where  N  is  the 
number  of  persons  to  be  provided  for.  See  Art.  9. 

36.  Air  Required  per  Hour  as  a  Heat  Carrier:  —  A  safe 
temperature  t,  of  the  circulating  air  as  it  leaves  the  heat 
register,  is  130  degrees.  This  may  at  times  reach  140  de- 
grees but  it  is  not  well  to  use  the  higher  value  in  the 
calculations.  If,  as  is  nearly  always  the  case,  the  room 
air  temperature,  *',  is  70  degrees,  the  incoming  air  will 
drop  in  temperature  through  60  degrees  and,  since  one  cubic 
foot  of  air  can  be  heated  through  55  degrees  by  one  B.  t.  u. 
(see  Art.  27.),  it  will  give  off  60  -4-  55  =  1.09  (say  1.1)  B.  t.  u. 

Let  Q  =  cubic  feet  of  air  per  hour  as  a  heat  carrier;  H 
=  total  heat  loss  in  B.  t.  u.  per  hour  by  formula;  t  =  tern- 
perature  of  the  air  at  the  register;  and  f  =  temperature  of 
the  room  air;  then 

0   =       55g  (14) 

t    -     *' 

Rule.  —  To  find  the  cubic  feet  of  air  necessary  to  carry  the  heat 
to  the  rooms,  multiply  the  heat  loss  calculated  by  formula  by  fifty- 
ftve  and  divide  by  the  difference  between  the  register  and  the  room 
temperatures. 

For  ordinary  furnace  work  this  becomes 

H 


Now  if  this  air  is  not  allowed  to  escape  from  the  building, 
Fig.  13,  but  is  taken  back  to  the  furnace  and  recirculated, 
the  only  loss  of  heat  will  be  H,  that  calculated  by  the 
formula;  but  as  a  matter  of  fact,  air  thus  used  would  soon 
become  contaminated  and  wholly  unfit  for  the  occupants  to 
breathe,  hence,  it  is  customary  to  exhaust  through  ventil- 
ating flues,  either  a  part  or  all  of.  the  air  sent  from  the 
furnace.  This  makes  an  additional  loss  of  heat  from 
the  building  corresponding  to  the  drop  in  degrees  from  70 
to  that  of  the  outside  air.  Let  the  temperature  of  the  out- 
side air,  to,  be  0  degrees,  then  the  resulting  heat  loss  would 
be  (see  also  Art.  110  on  blower  work.)  H'  =  H  plus  (f  —  to) 
divided  by  55  and  multiplied  by  the  amount  of  air  intro- 
duced for  ventilation.  Stated  as  a  formula  for  the  special 
conditions,  this  becomes 

H'  -   H   +    1.27    0,  (15) 


FURNACE   HEATING  55 

Take  for  illustration  the  Sitting  Room,  Pig.  15,  and 
consider  it  under  three  conditions  on  a  zero  day:  first,  when 
all  the  air  is  recirculated;  second,  when  only  enough  air  is 
exhausted  to  give  good  fresh  air  for  ventilation;  third, 
when  all  the  air  is  exhausted.  Under  the  first  case  the  loss 
H,  by  formula  is,  say,  14000  B.  t.  u.  per  hour  and  no  other 
loss  is  experienced.  In  the  second  case,  let  three  people  oc- 
cupy the  room  and  allow  1800  cubic  feet  of  fresh  air  per  hour 
for  each  person,  or  a  total  of  5400  cubic  feet  per  hour,  then 
the  total  heat  loss  from  the  room  will  be,  Formula  13, 
14000  +  5400  X  70  -r-  55  =  20873,  say  21000  B.  t.  u.  The 
third  case,  where  all  the  air  is  exhausted,  gives  14000  -j-  1.1 
=  12727  cubic  feet  of  fresh  air  exhausted  at  70  degrees, 
which  requires  the  same  amount  of  fresh  air  being  raised 
from  zero  to  70  degrees  to  replace  it.  This  necessitates  the 
application  of  12727  X  70  -r-  55  =  16198  B.  t.  u.  additional, 
or  a  total  heat  loss  of  30198,  say  30000  B.  t.  u.  per  hour. 

The  second  condition  is  that  which  would  be  found  most 
satisfactory.  It  is  evident  from  inspection  that  the  cubic 
feet  of  air  necessary  as  a  heat  carrier  will  supply  excessive 
air  for  ventilation  in  the  average  residence,  and  the  de- 
signer need  not  necessarily  consider  the  amount  of  air  for 
ventilation  except  as  he  wishes  to  investigate  the  size  of 
the  furnace,  the  amount  of  coal  burned  or  the  cost  of 
heating;  the  latter-being  in  direct  proportion  to  the  respect- 
ive total  heat  losses.  (See  also  Art.  60.) 

APPLICATION. — Referring  to  Table  IX,  page  63,  the  calcu- 
lated amount  of  air  per  hour  for  the  various  rooms  and  for 
the  entire  building  may  be  found. 

37.  Is  this  Amount  of  Air  Sufficient  for  Ventilation  if 
Taken  from  the  Outside? — Take  the  13  X  15  X  10  foot  sitting 
room,  Fig.  15.  Let  the  estimated  heat  loss  be  14000  B.  t.  u. 
per  hour,  then  Q  =  12727  cubic  feet.  With  a  room  volume 
of  1950  cubic  feet,  the  air  will  change  6.5  times  per  hour, 
and,  allowing  1800  cubic  feet  of  air  per  person,  will  supply 
seven  people  with  good  ventilation"  if  fresh  air  be  used. 
Stated  as  a  formula,,  this  would  be 

H  n 

N  = = approx.  (16) 

1.1  X  1800  2000 

As  a  matter  of  fact,  ventilation  for  half  this  number  would 
be  ample  in  an  ordinary  residence  room  excepting  on  extraor- 


56  HEATING  AND  VENTILATION 

dinary  occasions.  So  it  would  seem  that  the  subject  of 
ventilating  air  will  be  more  than  taken  care  of  if  the  ducts 
and  registers  are  planned  to  carry  air  for  heating  purposes 
only. 

38.  Given  the  Heat  Loss  H  and  the  Volume  of  Air  Q'  for 
any  Room,  to  find  /,  the  Temperature  of  the  Air  Entering  at 
the  Register: — If  for  any  reason  Q  is  not  sufficient  for  ven- 
tilation,   then   more   air   must   be   sent   to   the   room  and   the 
temperature    dropped    correspondingly   to   avoid    overheating 
the  room.     Let  Q'  —  total  volume  of  air  per  hour,  including 
extra    air    for    ventilation,    measured    at    the    register,    then 

55  H 

t  =  70  +     (17) 

Q' 

Rule. — When  it  is  necessary  for  ventilation  purposes  to  circu- 
late more  air  than  that  calculated  from  the  heat  loss  formula,  then 
the  temperature  at  the  register  will  be  found  ~by  adding  to  seventy 
degrees  the  amount  found  by  multiplying  the  heat  loss  by  fifty-five 
and  dividing  by  the  cubic  feet  of  ventilating  air. 

APPLICATION. — Suppose  it  were  necessary  to  send  18000 
cubic  feet  of  fresh  air  to  this  sitting  room  per  hour  to  ac- 
commodate ten  people,  the  temperature  of  the  air  at  the 
register  should  be 

55  X  14000 

t  =  70  H =  113°. 

18000 

39.  Net    Heat    Registers: — The    velocity    of    the    air    v, 
as  it   leaves   the   heat  register,   varies  from  3   to   4  feet  per 
second    according    to    different    designers.      The    first    figure 
is  objected   to  by   some   because   it  gives   too   large  register 
areas;  while  the  latter  value  is  cla-imed  to  be  great  enough 
that   the   occupants   of  the   room   will    notice   the   movement 
of  the  air.     Practice  no  doubt  tends  to  the  higher  velocity. 
Most    heat    registers    in    residences    are    placed    at    the    floor 
line.      If,    however,    they   be    placed    above    the   heads    of   the 
occupants  of  the  room  (see  Art.  102),  higher  velocities  than 
the  ones  named  can  be  used.     The  general  formula  for   net 
registers  is 

H  X  55  X  144 

N.   H.   R.   =  (18) 

(t  —  t')  X  r  X  3600 

Rule. — To  find  the  square  inches  of  net  Jteat  register,  multiply 
the  heat  loss  calculated  by  formula  by  two  and  two-tenths  and  di- 
vide by  the  product  of  the  velocity  in  feet  per  second  times  the 
difference  in  temperature  between  the  register  and  the  room  air. 


FURNACE   HEATING  57 

Assuming  a  mean  velocity  of  3.5  feet  per  second,  and 
60  degrees  drop  in  temperature  from  the  register  to  the 
room,  then  the  square  inches  of  net  register  for  any  room 
are  found  by  the  formula: 

nx  55  X144 

N.  H.  R.  = =  .01  H  (19) 

60  X  3.5  X  3600 

40.  Net  Vent  Registers: — Vent  registers  should   be   put 
In  with  any  furnace  plant,  although  this  is  not  always  done. 
In  order  that  any  room  may  be  heated  properly,  it  is  abso- 
lutely  necessary  that  the   cold  air  in  the  room   be  allowed 
to  escape  to  give  room  for  the  heated  air  to  come  in.     This 
in   some   cases   is   done   by  venting  through   doors,   windows 
or    transoms.      A    tightly    closed    room    cannot    be    properly 
heated   by   a   furnace. 

If  all  the  air  were  to  pass  out  the  vent  register  at  the 
same  velocity  as  it  entered  through  the  heat  register,  the 
area  of  the  vent  register  would  be  to  the  area  of  the  heat 
register  as  the  ratio  of  the  absolute  temperatures  of  the 
leaving  and  entering  air;  that  is,  the  area  of  the  vent 
register  —  .9  of  the  area  of  the  heat  register.  As  a  matter 
of  fact,  since  some  of  the  air  leavesi  the  room  through  other 
openings,  the  vent  register  need  not  be  so  large.  Practice 
has  decided  this  area  to  be  about 

N.  Y.  R.  =  .008  H  =  .8  N.  H.  R.  (20) 

41.  Gross  Register  Area: — The  nominal  size,  or  catalog 
size,  of  the  register  is  usually  stated  as  the  two  dimensions 
of   the    rectangular   opening   into    which   It    fits,    and    varies 
from  1.5  to  2  times  the  net  area.     The  larger  value  is  prob- 
ably the  safer  to  follow   unless  the  exact  value  be  known 
for   any    special    make    of    register.      Floor    registers    have 
heavier  bars  and  consequently  for  the  same  net  area   have 
somewhat  larger  gross  area. 

O.  R.  =  (1.5  to  2)  times  the  net  register  (21) 

Round  registers  may  be  had  if  desired.     Register  sizes  may 
be  found  in  Tables  17  and  19,  Appendix. 

42.  Heat  Stacks: — To  get  the  proper  sizes  of  the  stacks 
in  any  heating  system  is  a  very  important  part  of  the  de- 
sign of  that  system.     By  some  designers  the  cross  sectional 
area  is  taken  roughly  as  a  certain  ratio  to  that  of  the  net 


58  HEATING  AND  VENTILATION 

register.  This  has  been  quoted  anywhere  from  50  to  90 
per  cent.  Such  wide  variations  between  extremes  of  air 
velocity  should  certainly  require  careful  application.  Prof. 
Carpenter  in  H.  and  V.  B.  Arts.  54  and  141,  suggests  4,  5 
and  6  feet  per  second  respectively,  as  the  air  velocities  for 
the  first,  second  and  third  floors.  Mr.  J.  P.  Bird,  in  the 
"Metal  Worker"  of  Dec.  16,  1905,  uses  280,  400  and  500  feet 
per  minute,  which  is  approximately  4.5,  6.5  and  8  feet  per 
second  under  like  conditions.  The  formula  for  cross  sec- 
tional area  of  the  heat  stack,  from  formula  19,  then  becomes, 
if  the  velocities  are  4,  5.5  and  7  feet  per  second, 


H  X  55  X  144  r  0091  JJ  1st    floor") 

H.   S.  =  =  •{  .  0066  H  2nd  floor  j-    (22) 

60  X  (4,  5.5  or  7)   X  3600          1. 0052  H  3rd  floorj 

Rule. — See  rule  under  net  heat  registers  icith  changed  value 
for  velocity. 

The  air  velocity  in  the  stack  is  based  upon  the  formula 
v  =  V207T,  where  h  =  (effective  height  of  stack)  X  (f  —  «')  -r 
(460  +  *') ;  v  is  in  feet  per  second;  t  is  the  temperature  of 
the  stack  air  and  t'  is  the  temperature  of  the  room  air. 
The  calculated  results  from  this  formula  are  much  higher 
than  those  obtained  in  practice  because  of  the  shape  of 
cross  sections  of  the  stack,  the  friction  of  its  sides  and  the 
abrupt  turns  in  it. 

From  the  basis  of  the  net  register  (figured  at  3.5  feet 
per  second)  the  two  quotations  by  Carpenter  a..d  Bird  give 
heat  stack  areas  as  follows:  first  floor,  80  to  88  per 
cent.;  second  floor,  55  to  70  per  cent.;  and  third  floor,  44  to 
60  per  cent.  Good  sized  stacks  are  always  advisable  (see 
Art.  55),  but  because  of  the  limited  space  between  the  stud- 
ding it  becomes  necessary  at  times  to  put  in  a  stack  that 
is  too  small  or  to  increase  the  thickness  of  the  wall,  a  thing 
which  the  architect  is  occasionally  unwilling  to  do.  From 
the  above  figures,  checked  by  existing  plants  that  are 
working  satisfactorily,  the  following  approximate  figures, 
reduced  to  the  basis  of  the  net  heat  register  area,  will  no 
doubt  give  good  results. 

r.8     times  the  net  heat  register.  1st    floor  ^ 
H     S     =H  .66  times  the  net  heat  register.   2nd  floor  W       (23) 
1.5     times  the  net  heat  register.  3rd   floorj 

43.  Vent  Stacks:— 7.  8.  —  .B  H.  8.  (24) 

44.  Leader  Pipes:— Since  all  the  air  that  passes  through 
the    stacks    must   pass    through    the    leader   pipes,    it    seems 


FURNACE    HEATING  59 

reasonable  to  .assume  that  the  areas  of  the  two  would  be 
equal.  It  must  be  remembered,  however,  that  the  stacks, 
because  of  their  vertical  position,  offer  less  resistance  in 
friction,  while  on  the  other  hand  the  leader  pipes,  being 
nearly  horizontal  and  having  more  crooks  and  turns  in 
them,  will  have  considerable  friction  and  will  consequently 
retard  the  air  to  a  greater  degree.  There  will  also  be  some 
loss  of  temperature  in  the  air  as  it  passes  through  the 
leader  pipes,  consequently  the  volume  of  air  entering  the 
leader  from  the  furnace  will  be  greater  than  that  going 
up  the  stack. 

It  would  be  well,  from  the  above  reasons,  to  make  the 
area  of  the  leader  pipes 

L.  P.  =  (1.1  to  1.2)  times  the  stack  area,  (25) 

the  exact  figures  to  depend  upon  the  length  and  inclination 
of  the  leader  and  the  selection  of  the  diameter  of  the  pipe. 

45.  Fresh  Air  Duct: — The  area  of  the  fresh  air  duct  is 
determined  largely  by  experience  as  in  the  case  of  the  vent 
register.     It  is  generally  taken 

F.  A.  D.  =  .8  times  the  total  area  of  the  leaders.        (26) 

Assume  the  average  velocity  of  the  air  in  the  leaders  to  be 
6  feet  per  second  and  the  area  of  the  fresh  air  duct  to  be 
as  shown  above,  then,  if  the  air  in  each  were  of  the  same 
temperature,  the  velocity  in  the  fresh  air  duct  would  be 
G  -f-  .8  —  7.5  feet  per  second;  but  since  the  temperatures 
are  different  the  velocities  will  be  in  proportion  to  the  ab- 
solute temperatures.  Hence  it  is,  at  0  degrees,  .78  X  7.5  •= 
5.8;  at  25  degrees,  .82  X  7.5  =  6.2;  and  at  50  degrees,  .88 
X  7.5  =  6.6  feet  per  second.  It  is  seen  by  this,  that  al- 
though the  area  of  the  fresh  air  duot  is  contracted  to  80 
per  cent,  of  that  of  the  leaders,  the  velocity  is  in  all 
cases  below  that  of  the  leaders.  It  is  always  well  to  have 
a  fresh  air  duct  that  is  large  in  cross  sectional  area  and 
free  from  obstructions  and  sharp  turns. 

46.  Grate  Area: — The  grate  area  of  a  furnace   is  esti- 
mated from   the   total   heat   lost   from  the    building,   figured 
on  a  basis  of  a  certain  degree  of  ventilation.     In  obtaining 
the  grate  area  it  is  necessary  to  assume  the  quality  of  the 
coal,    the   efficiency   of   the   furnace   and   the   pounds   of  coal 
burned  per  hour  per  square   foot  of  grate.     The  quality  of 


60  HEATING  AND  VENTILATION 

coal  selected  would  be  between  12000  and  14000  B.  t.  u.  per 
pound  as  shown  in  Table  14,  Appendix.  The  efficiency  of 
the  average  furnace  is  about  60  per  cent.,  and  the  coal 
burned  per  square  foot  of  grate  per  hour  ranges  from  3  to 
7  pounds.  Concerning  the  last  point  there  may  be  a  wide 
difference  of  opinion.  Higher  temperatures  in  the  combus- 
tion chamber  are  conducive  to  economy,  because  of  the 
radiant  heat  of  the  fire;  hence,  to  reduce  the  size 
of  the  fire  pot,  and  fire  small  amounts  of  coal  with 
greater  frequency  would  seem  to  be  the  ideal  way.  On 
the  other  hand,  with  high  temperatures  in  the  combustion 
chamber,  the  loss  up  the  chimney  is  increased.  Probably 
the  one  factor  which  is  most  effective  in  settling  this  point 
is  the  inconvenience  of  frequent  firing.  Furnaces  are 
charged  from  two  to  four  times  each  twenty-four  hours. 
This  requires  a  good  sized  fire  pot  and  a  possibility  of 
banking  the  fires.  To  allow  5  pounds  per  hour  is  probably 
as  good  an  average  as  can  be  made  for  most  coals  in  fur- 
nace work. 

Let  H'  =  total  heat  loss  from  the  building  including 
ventilation  loss;  E  =  efficiency  of  the  furnace;  /  =  value  of 
coal  in  B.  t.  u.  per  pound;  and  p  =  pounds  of  coal  burned 
per  square  foot  of  grate  per  hour;  then  the  formula  for  the 
square  inches  of  grate  area  is 

H'  X  144 

0.  A.  =  (27) 

E  X  /  X  p 

Rule. — To  find  the  square  inches  of  grate  area  for  any  furnace, 
multiply  the  total  heat  loss  from  the  building  per  hour  by  one 
hundred  and  forty-four  and  divide  l>y  the  quantity  found  by  multi- 
plying the  total  pounds  of  coal  burned  per  hour  by  the  heat  value  of 
the  coal  and  the  efficiency  of  the  furnace. 

APPLICATION. — In  the  typical  illustration,  the  total  heat  loss 
on  a  zero  day  by  formula  is,  say,  100000  B.  t.  u.  per  hour. 
This  will  require  90909  cubic  feet  of  air  as  a  heat  carrier. 
Assuming  as  a  maximum  that  10  people  will  be  in  the 
house  and  that  they  will  need  18000  cubic  feet  of  fresh  air 
per  hour  for  ventilation,  this  air  will  carry  away  approx- 
imately 22900  B.  t.  u.  per  hour,  making  a  total  heat  loss 
from  the  building  of  122900  B.  t.  u.  per  hour.  Now,  if  the 
furnace  is  60  per  cent,  efficient  and  burns  5  pounds  of 
14000  B.  t.  u.  coal  per  hour  per  square  foot  of  grate,  we 
will  have 

122900  X  144 

0,  4.  =:  _ =  421  square  inches  =  23.2  inches 

.60  X  14000  X  5 


FURNACE   HEATING  61 

diameter.  With  coal  at  13000  B.  t.  u.  per  pound,  the  grate 
would  be  454  square  inches  or  24  inches  diameter.  In  either 
case  a  24  inch  grate  would  be  selected.  With  .the  assump- 
tions as  made  above,  the  formula  becomes  G.  A.  =  .0035  H' 
for  the  better  grade  of  coal,  and  G.  A.  =  .0037  H'  for  the 
poorer  grade,  from  which  the  following  approximate  form- 
ula may  be  taken: 

G.  A.  square  inches  =  .0036  H'  (28) 

47.  Healing  Surface: — The  amount  of  heating  surface 
to  be  required  in  any  furnace  is  rather  an  indefinite  quantity. 
Manufacturers  differ  upon  this  point.  Some  standard  may 
soon  be  looked  for  but  at  present  only  rough  approximations 
can  be  stated.  One  of  the  chief  difficulties  is  in  determin- 
ing what  is,  or  what  is  not,  heating  surface.  Some  quota- 
tions no  doubt  include  some  surface  in  the  furnace  that  is 
very  inefficient.  In  estimating,  only  prime  heating  surface 
should  be  considered,  i.  e.,  such  plates  or  materials  having 
•direct  contact  with  the  heated  flue  gases  on  one  side  and 
the  warm  air  current  on  the  other.  If  these  plates  trans- 
mit K,  B.  t.  u.  per  square  foot  per  degree  difference  of  tem- 
perature, tz,  per  hour;  if,  also,  one  square  foot  of  grate 
gives  to  the  building  E  X  /  X  p  B.  t.  u.  per  hour,  there  will 
be  the  following  ratio  between  the  heating  surface  and 
grate  surface: 

B.  8.  E  f  p 


G.  8.  Ktz 


(29) 


APPLICATION. — Let  the  value  K  tz  be  2500,  as  suggested  by 
W.  G.  Snow,  Trans.  A.  S.  H.  &  V.  E.,  1906,  page  133,  and 
with  the  same  notations  as  in  Art.  46  obtain 

X  14000  X  5 

—  =  17 


2500 

In  practice  this  ratio  varies  anywhere  between  12  and  30. 

In  the  investigations  being  made  by  the  Federal  Fur- 
nace League  their  furnaces  show  an  average  of  1%  square 
feet  of  direct  heating  surface  and  1  square  foot  of  indirect 
heating  surface  per  pound  of  coal  burned  in  the  furnaces 
per  hour,  making  a  total  of  2%  square  feet  of  heating  sur- 
face per  pound  of  coal  burned  per  hour.  The  average  size 
of  the  furnaces  submitted  for  tests,  and  probably  the  aver- 
age size  of  furnaces  used  in  actual  practice,  have  a  top  fire- 


62  HEATING  AND  VENTILATION 

pot  diameter  of  24  inches  and  a  bottom  fire-pot  diameter  of 
21  inches,  making  an  average  fire-pot  diameter  of  221/£  inches 
and  an  average  cross-sectional  area  of  2.83  square  feet. 
The  average  depth  of  pot  in  this  size  of  furnace  is  about 
13y2  inches,  and  for  the  purpose  of  rating  under  the  Fed- 
eral System  would  burn  7.2  pounds  of  coal  per  hour  per 
square  foot  of  average'  fire-pot  cross-section,  making  the 
ratio  per  square  foot  of  grate  surface  about  81A  pounds  of 
coal  per  hour.  This  gives  a  ratio  of  heating  surface  to 
grate  surface  of  approximately  20  to  1. 

48.  Application  of  the  Above  Formulas  to  a  Ten  Room 
Residence: — In  every  design  the  calculations  should  be  made 
very  complete  and  the  results  tabulated  for  easy  reference 
and  as  a  means  of  comparison.  Such  a  tabulation  is  shown 
in  Table  IX,  giving  all  the  calculated  quantities  necessary  in 
the  installation  of  the  furnace  system  illustrated  in  Figs. 
14,  15  and  16.  The  value  of  so  condensing  the  work  will  be 
readily  apparent.  The  tabulation  of  the  values  used 
for  the  various  terms  of  the  formula  facilitates  checking' 
and  the  detection  of  errors.  Plans  should  be  carefully 
drawn  to  scale  and  accompanied  by  a  sectional  elevation. 
Th.e  scale  should  be  as  large  as  can  conveniently  be  made. 
The  location  of  the  building  with  reference  to  the  points 
of  the  compass  should  always  be  given,  as  well  as  the 
heights  of  ceilings  and  the  principal  dimensions  of  each 
room.  There  will  be  a  wide  variety  of  practic3  in  making 
allowance  for  exposure,  floors,  ceilings,  closets  and  small 
rooms  not  considered  of  sufficient  importance  to  have  inde- 
pendent heat.  The  personal  element  enters  into  this  part  of 
the  work  very  largely.  Such  points  as  these  are  left  to 
the  discretion  of  the  designer  who,  after  having  had  con- 
siderable experience  is  able  to  judge  each  case  very  closely. 


FURNACE   HEATING 


63 


TABLE    IX. 

Formula.  H  =  ((?  +    .25  W  +    .02  nO)    70 


d 

!H 

h 

!H 

SH 

a§ 

«»o 

ti 

2 

_o 

| 

1 

2 

I 

C  o 

**W 

3" 

£ 

,d 

3 

P,o3 

?w 

!•" 

§W 

• 

I" 

I" 

^ 

^ 

33 

s 

02 

3 

i 

.d 
O 

,d 

O 

.d 
O 

J3 

O 

1 

I 

G 

38 

28 

42 

28 

99 

42 

£8 

9S 

QS 

14 

315 

-25  TF 

85 

28 

52 

65 

73 

45 

63 

9« 

80 

17 

481 

.02  ?t  C 

78 

81 

78 

104 

35 

36 

81 

99 

<>6 

n  . 

2 

2 

2 

2 

3 

1 

1 

1 

1 

9 

14000 

10800 

18250 

11900 

14000 

9400 

9850 

6600 

*S600 

4400 

99800 

a 

12727 

9818 

12045 

10818  19797 

8544 

8954 

6000 

5091 

1000 

Area  of  Net  Heat  Register 

140 

108 

132 

119 

140 

94 

98 

66 

56 

44 

..... 

Heat  Reg  star  Size.  

14x16 

12x14 

14x16 

12x14 

14x16 

12x12 

12x12 

Qxl? 

8vlO 

8x10 

Area  of  Heat  Stack... 

61 

64 

43 

86 

?8 

Area  of  Leader  

100 

77 

94 

85 

100 

67 

70 

47 

40 

81 

711 

Area  of  Net  Vent  Register 

112 

86 

106 

95 

112 

75 

78 

53 

45 

85 

Vent  Register  Size  

12x14 

10x12 

12x14 

12x12 

12x14 

10x12 

10x12 

8x10 

8x10 

8x8 

Area  of  Vent  Stack  

67 

52 

64 

60 

67 

45 

48 

32 

27 

22 



• 

| 

o> 

b 

>> 

2 

i 

«a 

o> 

«• 
o> 

O 

& 

d 

^ 

P 

0 

O 

| 

o 

a 

& 
O 

5 

8 

£ 

1 

O. 

& 

• 

£% 

41 

o> 

§ 

<2 

0 

8 

£ 

A 

"S 

d  •- 

§ 

02 

«; 

a 

+J 

d 

Remarks 

for  cold  fl 

10  per  cer 
exposure 

"5 
hi 

& 

0 

15  per  cen 
i*  and  expc 

for  floor  a 
econd  floe 

10  per  ct.  \ 

£ 

* 
1 

10  per  cer 
exposure 

oset  to  ro< 

10  per  ce 
exposure 

a 

!! 

1 

O 

ra 

2% 

II 

I 

o 

Id 

£ 

o 

!! 

o 

*J 

¥2 

5S 

«! 

5 

•< 

i 

<\ 

| 

1 

1 

4 

<j 

Diameter  of  grate  allowing  ventilation  for  ten  people  = 
24  inches.  Cold  air  duct  =  569  square  inches  =  18  X  32  inches. 

In  selecting  the  various  stacks  and  leaders  it  would  be 
well  to  standardize  as  much  as  possible  and  avoid  the  extra 
expense  of  installing  so  many  sizes.  This  can  be  done  if 
the  net  area  is  not  sacrificed. 


64 


HEATING  AND  VENTILATION 


I 


FOUNDATION  PLAN. 
.    Ceiling  6'. 

Fig.  14. 


FURNACE   HEATING 


1 


FIRST  FLOOR  PLAN. 
Ceiling  10'. 
Fig.  15. 


HEATING  AND  VENTILATION 


SECOND  FLOOR  PLAN. 
Ceiling  9'. 

Fig.  16. 


CHAPTER  V. 


FURNACE  HEATING  AND  VENTILATING. 


SUGGESTIONS     ON     THE     SELECTION     AND    INSTALLATION     OF 
FURNACE  HEATING  PARTS. 

49.  Selection  of  the  Furnace: — In  selecting  a  furnace 
for  residence  use  or  other  heating  service,  special  attention 
should  be  paid  to  the  following  points:  easy  movement  of 
the  air,  arrangement  and  amount  of  heating  surface,  shape 
and  size  of  the  fire-pot,  method  of  feeding  fuel  to  the  fire 
and  type  and  size  of  the  grate.  The  furnace  gases  and  the 
air  to  be  heated  should  not  be  allowed  to  pass  through  the 
furnace  in  too  large  a  unit  volume  or  at  too  high  a  velocity. 
The  gases  should  be  broken  up  in  relatively  small  volumes, 
thus  giving  an  opportunity  for  a  large  heating  surface. 
Concerning  the  gas  passages  themselves,  it  may  be  said 
that  a  number  of  small,  thin  passages  will  be  found  more 
efficient  than  one  large  passage  of  equal  total  area.  This 
is  plainly  shown  in  a  similar  case  by  comparing  the  effi- 
ciency of  the  water-tube  or  tubular  boiler  with  that  of 
the  old  fashioned  flue  boiler;  i.  e.,  a  large  heating  surface 
is  of  prime  importance.  Again,  it  is  desirable  that  the 
total  flue  area  within  the  furnace  should  be  great  enough 
to  allow  the  passage  of  large  volumes  of  air  at  low  velocities, 
rather  than  small  volumes  at  high  velocities.  This  permits 
of  less  forcing  of  the  fire  and  consequently  lowers  the  tem- 
perature of  the  heating  surface.  The  latter  point  will  be 
found  valuable  when  it  is  remembered  that  metal  at  high 
temperatures  transmits  through  its  body  a  greater  amount 
of  impure  gases  from  the  coal  than  when  at  low  tempera- 
tures. Concerning  velocities,  it  may  be  said  that  on  account 
of  the  low  rate  of  transmission  of  heat  to  or  from  the 
gases,  long  flue  passages  are  necessary,  so  that  gases  mov- 
,ing  at  a  normal  rate  will  have  time  to  give  off  or  to  take 
up  a  maximum  amount  of  heat  before  leaving  the  furnace. 

Air  is  heated  chiefly  by  actual  contact  with  heated  sur- 
faces and  not  much  by  radiation.  Consequently,  the  ef- 
ficiency of  a  furnace  is  increased  when  it  is  designed  so 
that  the  gases  and  air  in  their  movement  impinge  perpen- 


6S 


HEATING  AND  VENTILATION 


dicularly  upon  the  heated  surfaces  at  certain  places.  This 
point  should  not  be  so  exaggerated  that  there  would  be 
serious  interference  with  the  draft.  The  efficiency  is  also 
increased  if  the  general  movement  of  the  two  currents  be 
in  opposite  directions. 

Furnaces  for  residences  are  usually  of  the  portable  type. 
Fig.  17,  the  same  being  enclosed  in  an  outer  shell  composed 
of  two  metal  casings  having  a  dead  air  space  or  an  asbes- 
tos insulation  between  them.  Some  of  the  larger  »ized 


Fig.   17. 

plants,  however,  have  the  furnace  enclosed  in  a  permanent 
casement  of  brick  work,  as  in  Fig,  18.  Each  of  the  two 
types  of  furnaces  give  good  results.  The  points  usually 
governing  the  selection  between  portable  and  permanent 
settings  are  price  and  available  floor  space. 

The  cylindrical  fire-pot  is  pro'bab'ly  better  than  a  con- 
ical or  spherical  one,  there  being  less  danger  of  the  fire 
clogging  and  becoming  dirty.  A  lined  fire-pot  is  better 
than  an  unlined  one,  because  a  hotter  fire  can  be  maintained 
in  it  with  less  detriment  to  the  furnace.  There  is  of  course 
a  loss  of  heating  surface  in  the  lined  pot,  and  in  some  forms 


FURNACE   HEATING 


69 


of  furnaces  the  fire-pot  Is  unlined  to-  obtain  this  increased 
heating  surface.  It  seems  reas'onable  to  assume,  however, 
that  the  lined  pot  is  longer  lived  and  contaminates  the  air 

supply  less. 


Fig.   18. 


Fig.    19, 


70 


HEATING  AND  VENTILATION 


Some  form  of  shaking  or  dumping  grate  should  be  se- 
lected, as  a  stationary  grate  is  far  from  satisfactory.  Care 
should  be  exercised  also,  in  the  selection  of  the  movable 
grate,  as  some  forms  not  only  stir  up  the  fire  but  permit 
much  of  it  to  fall  through  to  waste  when  being  operated. 

The  fuel  is  fed  to  the  fire-pot  from  the  door  above  the 
fire.  This  is  called  a  top-feed  furnace.  In  some  forms,  how- 
ever, the  fuel  is  fed  up  through  the  grate.  This  is  called 
the  under-feed  furnace,  Fig,  19,  and  is  rapidly  gaining  in 
favor.  The  latter  type  requires  a  rotary  ring  grate  with 
the  fuel  entering  up  through  its  center. 

The  size  of  the  furnace  may  be  obtained  from  the  estimated 
Treating  capacity  in  cubic  feet  of  room  space  as  given  in  the 
sample  Table  18,  Appendix.  Another  and  perhaps  a  bet- 
ter way,  and  one.  that  serves  as  a  gocd  check  on  the  above, 
is  to  select  a  furnace  from  the  calculated,  grate  area.  See  Art. 
46.  Having  selected  the  furnace  by  the  grate  area,  check 
this  with  the  table  for  the  estimated  heating  capacity 
and  the  heating  surface  to  see  If  they  agree. 

What  is  known  as  a  combination  heater  is  shown  in 
Fig.  20.  It  is  used  for  heating  part  of  the  rooms  of  a  resi- 
dence by  warm  air,  as  in 
regular  furnace  work,  and 
the  remainder  of  the  rooms 
by  hot  water.  In  this 
manner,  rooms  to  be  ven- 
tilated as  well  as  heated 
may  be  connected  by  the 
proper  stacks  and  leaders 
to  •  the  warm  air  deliveries 
of  such  a  combination 
heater,  while  rooms  requir- 
ing less  ventilation  or  heat 
only  may  have  radiators 
installed  and  connected  to 
the  flow  and  return  pipes 
shown  in  the  figure.  Also, 
because  of  the  difficulty 
in  heating  certain  exposed 
rooms  with  warm  air,  these 
rooms  may  be  supplied  by 
the  positive  heat  of  the 
more  reliable  water  circulation. 


FURNACE   HEATING  71 

50.  Location     of     Furnace: — Wljere     other    things    do 
not   interfere,   a   furnace    should   be   set   as   near   the    center 
of  the  house   plan  as   possible.     Where  this   is  not  wise   or 
possible,  preference  should  be  given  to  the  colder  sides,  say 
the  north  or  west.     In  any  case,  it  is  advisable  to  have  the 
leader  pipes  as   near  the   same  length  as   can  be   made.  The 
length    of   the    smoke   pipe   should   be   as    short   as   possible, 
but  it  will  be  better  to  have  a  moderately  long  smoke  pipe 
and  obtain  a   more  uniform   length  of  leader  pipes  than  to 
have   a    short   smoke    pipe    and    leaders    of    widely    different 
lengths. 

The  furnace  should  be  set  low  enough  to  get  a  good 
upward  slope  to  the  leaders  from  the  furnace  to  their  re- 
spective stacks.  This  should  be'  not  less  than  one  inch  per  foot 
of  length  and  more  if  possible.  These  leader  pipes  should  be 
dampered  near  the  furnace. 

The  location  of  the  furnace  will  call  forth  the  best 
judgment  of  the  designer,  since  the  right  or  wrong  decis- 
ion here  can  make  or  mar  the  whole  system  more  com- 
pletely than  in  any  other  manner. 

51.  Foundation: — All    furnaces    should    have    directions 
from  the  manufacturer  to  govern  the  setting.     Each  type  of 
furnace    requires    a    special    setting    and    the    maker   should 
best  be  able   to   supply  this  desired  information  concerning 
it.     Such  information  may  be  safely  fallowed.     In  any  case 
the  furnace  should  be  mounted  on  a  level  brick  or  concrete 
foundation  specially  prepared  and  well  finished  with  cement 
mortar  on  the  inside,  since  this  interior  is  in  contact  with 
the  fresh  air  supply. 

52.  Fresh  Air  Duct: — This  is  best  constructed   of  hard 
burned   brick,    vitrified   tile    or    concrete,    laid    in    four    inch 
walls    with    cement    mortar    and    plastered    inside    with    ce- 
ment plaster,  all  to  be  air  tight.     The  top  should  be  covered 
with    flag    stones    with    tight    joints.      The    riser    from    this, 
leading  to  the  outside  of  the  building,  may  be  of  wood,  tile 
or    galvanized    iron,    and    the    fresh    air    entrance    should    be 
vertically  screened.     The  whole  should  be  with  tight  joints 
and    so    constructed   as    to    be    free    from   surface    drainage,, 
dirt,    rats    and    other   vermin.      This    duct   may    be    made    of 
metal  or  boards  as  substitutes  for  the  brick,  tile  or  concrete. 
Board  construction  is  not  so  satisfactory,  although  it  is  the 
cheapest,  and  whenever  used  should  be  carefully  constructed. 


72 


HEATING  AND  VENTILATION 


In  addition  to  the  opening  for  the  admission  of  the 
fresh  air  duct,  another  opening  may  be  made  under  the 
furnace  for  the  purpose  of  admitting  the  duct  which  carries 
the  recirculated  air  from  the  rooms  to  the  furnace.  Both 
of  these  ducts  should  have  dampers  that  may  be  opened  or 


TURN 


FRONT 


FRONT 


FRONT 

Fig.  21. 

closed.  See  Figs.  13  and  21.  Both  ducts  should  also  be  provid- 
ed with  doors  that  can  be  opened  temporarily  to  the  cellar 
air.  Sometimes  it  is  desirable  to  have  two  or  more  fresh 
air  ducts  leading  from  the  different  sides  of  the  house  to  the 
furnace  so  as  to  get  the  benefit  of 
any  change  in  air  pressure  on  the 
outside  of  the  building. 

Proper  arrangements  may  be 
made  for  pans  of  clear  water  in  the 
air  duct  near  the  furnace  to  give 
moisture  to  the  air  current,  although 
only  a  small  amount  of  moisture 
will  be  taken  up  at  this  point.  In 
most  cases  where  moistening  pans 
are  used,  they  are.  installed  in  con- 
nection with  the  furnace  itself.  A 
good  way  to .  moisten  the  air  is  to 
have  moistening  pans  built  in  just 
behind  the  register  face,  Fig.  22. 
These  pans  are  shallow  and  should 
not  be  permitted  to  seriously  inter- 
fere with  the  amount  of  air  enter- 
ing through  the  register. 
53.  Recirculating  Duct: — A  duct  should  be  provided 
from  some  point  within  the  building,  through  the  cellar 
and  entering  into  the  bottom  of  the  furnace.  This  is  to  car- 


FURNACE    HEATING 


73 


ry  the  warm  air  from  the  room  back  to  the  furnace  to  be 
reheated  for  use  again  wiithin  the  building.  In  many  cases 
tin  or  galvanized  iron  is  used  for  the  material  for  the 
recirculating  pipe.  W'here  this  enters  the  furnace  it 
sihould  be  planned  with  sufficient  turn  so  that  the 
a-ir  would  be  projected  through  the  furnace,  ifchus 
placing  a  hindrance  to  the  fresh  cold  air  from  following 
back  through  this  pipe  to  the  rooms.  The  exact  location 
of  the  same  will  depend,  of  -course,  on  the  location  of  the 
register  installed  for  this  purpose.  The  construction  of  the 
duct  may  agree  with  the  similar  construction  of  the  fresh 
air  duct. 

64.      Leader    Pipes: — All    leader   pipes    should    be    round 
and   free    from    unnecessary    turns.      They    should    be    made 


Fig.  23. 


74 


HEATING  AND  VENTILATION 


from  heavy  galvanized  iron  or  tin  and  should  be  laid  to  an 
upward  pitch  of  not  less  than  one  inch  per  foot  of  length, 
and  more  if  it  can  possibly  be  given.  The  connections  with 
the  furnace  should  be  straight,  but  if  a  turn  is  necessary, 
provide  long  radius  elbows.  All  connections  to  risers  or 
stacks  should  be  made  through  long  radius  elbows.  Rect- 
angular shaped  boots  having  attached  collars  are  sometimes 
used,  but  these  are  not  so  satisfactory  because  of  the  im- 
pingement of  the  air  against  the  flat  side  of  the  stack;  also 
because  of  the  danger  of  the  leader  entering  too  far  into 
the  stack  and  thus  shutting  off  the  draft.  Leaders  should 
connect  to  the  first  floor  registers  by  long  radius  el- 
bows. Leader  pipes  should  have  as  few  joints  as  possible 
and  these  should  be  made  firm  and  air  tight.  Fig.  23  shows 
different  methods  of  connecting  between  leaders  and  stacks, 
also  between  leaders  and  registers. 

The  outside  of  all  leader  pipes  should  be  covered  to 
avoid  heat  loss  and  to  provide  additional  safety  to  the  plant. 
The  covering  is  usually  one  or  more  thicknesses  of  asbes- 
tos paper  or  mineral  wool. 

55.  Stacks  or  Risers: — The  vertical  air  pipes  leading  to 
the  registers  are  called  stacks  or  risers.  They  are  rect- 
angular or  oblong  in  section  and  are  usu- 
ally fitted  within  the  wall.  See  Fig.  24. 
The  size  of  the  studding  and  the  distances 
they  are  set,  center  to  center,  limit  the 
effective  area  of  the  stack.  All  stacks 
should  be  insulated  to  protect  the  wood- 
work. This  is  done  by  making  the  stack 
small  enough  to  clear  the  woodwork  by 
at  least  one-quarter  inch  and  then  wrap- 
ping it  with  some  non-conducting  material 
such  as  asbestos  paper  held  in  place  by 
wire. 

Another  way,  and  one  which  is  prob- 
ably more  satisfactory,  is  to  have  pat- 
ented double  walled  stacks  having  an  air 
space  between  the  walls  all  around.  The 
outside  wall  is  usually  provided  with  vent 
holes  which  allow  the  circulation  of  air 
between  the  walls,  thus  protecting  any 
one  part  from  becoming  overheated. -All 
•Fig.  24.  stacks  should  be  made  with  tight  joints 


FURNACE    HEATING  75 

and  should  have  ears  or  flaps  for  fastening  to  the  studding. 
Patented  sacks  are  made  in  standard  sizes  and  of  various 
lengths.  The  sizes  ordinarily  found  in  practice  are  about 
as  given  in  Table  19,  Appendix. 

A  stack  is  sometimes  run  up  in  a  corner  or  in  some 
recess  in  the  wall  of  a  room  where  its  appearance,  after 
being  finished  in  color  to  compare  with  that  of  the  room, 
would  not  be  unsightly.  This  is  necessary  in  any  case 
where  the  stack  is  installed  after  the  building  is  finished. 
This  method  is  desired  by  some  because  of  its  additional 
safety  and  because  more  stack  area  may  be  obtained  than 
is  possible  when  placed  within  a  thin  wall. 

All  stacks  should  be  located  in  partition  walls  looking 
toward  the  outside  or  cold  side  of  the  room.  This  protects 
the  air  current  from  excessive  loss  of  heat,  as  would  be  the 
case  in  the  outside  walls.  It  also  provides  a  more  uniform 
distribution  of  air. 

The  area  of  the  stack  best  adapted  to  any  given  room 
is  another  point  in  furnace  work  which  brings  out  a  wide 
diversity  of  practice.  Results  from  different  installations 
show  variations  as  great  as  50  per  cent.  This  is  not  so 
noticeable  in  the  first  floor  rooms  as  it  is  in  those  of  the 
second  floor.  In  a  great  many  cases  the  architect  specifies 
light  partition  walls  between  large  upper  rooms,  say,  four 
inch  studding  set  sixteen  inch  centers,  between  twelve  foot 
by  fifteen  foot  rooms,  heavily  exposed.  From  theoretical 
calculation  of  heat  losses,  these  rooms  require  larger  stacks 
than  can  be  placed  between  studding  as  stated;  however,  it 
is  very  common  to  find  such  rooms  provided  for  in  this  way. 
One  possible  excuse  for  it  may  be  the  fact  that  the  room  is 
designed  for  a  chamber  and  not  for  a  living  room.  Any 
sacrifice  in  heating  capacity  in  any  room,  even  though  it  be 
used  as  a  sleeping  room  only,  should  be  done  at  the  sug- 
gestion of  the  purchaser  and  not  at  the  suggestion  of  the 
architect  or  engineer.  Every  room  should  be  provided  with 
facilities  for  heat  as  though  it  were  to  be  used  as  a  living 
room  in  the  coldest  weather,  then  there  would  be  fewer 
complaints  of  defective  heating  plants  and  less  migrating 
from  one  side  of  the  house  to  the  other  on  cold  days. 

This  lack  of  heating  capacity  for  any  room  is  some- 
times overcome  by  providing  two  stacks  and  registers  in- 


76 


HEATING  AND  VENTILATION 


stead  of  one.  This  plan  is  very  satisfactory  because  one 
of  the  registers  may  be  shut  off  in  moderate  weather;  how- 
ever, it  requires  an  additional  expense  which  is  scarcely 
justified.  A  possible  improvement  would  be  for  the  archi- 
tect to  anticipate  such  conditions  and  provide  suitable 
partition  walls  so  that  ample  stack  area  could  be  put  in. 
The  ideal  conditions  will  be  reached  when  the  architect  act- 
ually provides  air  shafts  of  sufficient  size  to  accommodate 
either  a  round  or  a  nearly  square  stack.  When  this  time 
comes  a  great  many  of  the  furnace  heating  difficulties  wilJ 
have  been  solved. 

A  double  stack  supplying  air  to  two  rooms  is  some- 
times used,  having  a  partition  separating  the  air  currents 
near  the  upper  end.  This  practice  is  questionable  because 
of  the  liability  of  the  pressure  of  air  in  the  room  on  tho 
cold  side  of  the  house  forcing  the  heated  air  to  the  other 
room.  A  better  method  is  to  have  a  stack  for  each  room 
to  be  heated. 

56.  Vent  Stacks: — Vent  stacks  should  be  placed  on  the 
inner  or  partition  walls  and  'should  lead  to  the  attic.     They 
may   there   be   gathered   together   in   one   duct   leading   to   a 
vent  through   the  roof  if  desired. 

57.  Air  Circulation  Within  the  Room: — The  location   of 
the   heat  register,   relative  to   the  vent   register,  will   deter- 


Fig.   25. 


FURNACE   HEATING  77 

mine  to  a  large  degree  the  circulation  of  the  air  within  the 
room.  Fig.  25,  a,  b,  c  and  d,  shows  clearly  the  effect  of  the 
different  locations.  The  best  plan,  from  the  standpoint  of 
heating,  is  to  enter  the  air  at  a  point  above  the  'heads  of  the 
occupants  and  withdraw  it  from  the  floor  line,  at  or  near  the 
same  side  from  which  the  air  ent.ers.  This  gives  a  more  uni- 
form distribution  as  shown  by  the  last  figure.  It  is  doubtful, 
however,  if  this  method  will  give  the  best  ventilation  In 
crowded  rooms  where  the  foul  air  naturally  collects  at  the 
top  of  the  room.  Furnace  heating  is  not  so  well  cared  for 
in  this  regard  as  are  the  other  forms  of  indirect  heating,  the 
air  being  admitted  at  the  floor  line  and  required  to  find  Its 
own  way  out. 

58.  Fan-Furnace  Heating  System: — In  large  furnace 
installations  where  the  air  is  carried  in  long  ducts  that  are 
nearly,  if  not  quite,  horizontal,  and  where  a  continuous  sup- 
ply of  air  is  a  necessity  in  all  parts  of  the  building,  a  com- 
bination fan  and  furnace  system  may  be  installed.  These 
are  frequently  found  in  hospitals,  schools  and  churches.  Such 
a  system  may  be  properly  designated  a  mechanical  warm 
air  system.  In  comparison  with  other  mechanical  systems, 
however,  it  is  simpler  and  cheaper.  The  arrangement  may 
be  illustrated  by  Fig.  96  with  the  tempering  coils  omitted 
and  the  furnace  substituted  for  the  heating  coils.  The  fan 
should  always  be  between  the  air  inlet  and  the  furnace  so  as 
to  keep  a  slight  pressure  above  atmosphere  on  the  air  side 
and  thus  reduce .  the  leakage  of  the  fuel  gas  through  the 
joints  of  the  furnace.  By  this  arrangement  there  Is  less 
volume  of  air  to  be  handled  by  the  fan  and  a  smaller  sized 
fan  may  be  used. 

Fan-furnace  systems  may  be  set  in  multiple  if  desired,  1. 
e.,  one  fan  operating  in  connection  with  two  or  more  fur- 
naces. 

Fig.  26  represents  a  two-furnace  plant  showing  the 
fan  and  the  two  furnaces.  The  air  is  drawn  into  the  fresh 
air  room  through  a  grate  in  the  outside  wall  and  is  forced 
through  the  fan  to  the  furnaces  where  it  divides  and  passes 
up  through  each  furnace  to  the  warm  air  ducts.  Part  of 
the  fresh  air  from  the  fan  is  by-passed  over  the  top  of  the 
furnaces  and  is  admitted  to  the  warm  air  ducts  through 
mixing  dampers.  These  dampers  control  the  amount  of 
hot  and  >cold  air  for  any  desired  temperature  of  the  mix- 


HEATING  AND  VENTILATION 


Fig.    26. 


ture.  Temperature  control  may  be  applied,  also  air  washing 
and  humidifying  apparatus  can  be  installed  and  operated 
with  satisfaction.  Paddle  wheel  fans  are  preferred,  al- 
though the  disk  wheel  may  be  used  where  the  pipes  are 
large  and  where  the  air  must  be  carried  but  short  distances. 
For  fan  types  see  Chapter  X. 

59.  Suggestions  for  Operating:  Furnaces: — Furnaces  are 
designated  hard  coal  and  soft  coal,  depending  upon  the  type  and 
the  construction  of  the  grate,  hence  the  grade  of  coal  best 
adapted  to  the  furnace  should  be  used.  The  size  of  the  open- 
ings in  the  grate  should  determine  the  size  of  the  coal  used. 

Keep  the  fire-pot  well  filled  with  coal  and  have  it  evenly 
distributed  over  the  grate. 


FURNACE   HEATING  79 

Keep  the  fire  clean.  Clinkers  should  be  removed  from 
the  fire  once  or  twice  daily.  It  is  not  necessary  to  stir  the 
fire  so  completely  as  to  waste  the  coal  through  the  grate. 

When  replenishing  a  poor  fire  do  not  shake  the  fire,  but 
put  some  coal  on  and  open  the  drafts.  After  the  coal  is  well 
ignited  clean  the  fire. 

The  ash  pit  should  be  frequently  cleaned,  because  an 
accumulation  of  ashes  below  the  grate  soon  warps  the  grate 
and  burns  it  out. 

Keep  all  the  dampers  set  and  properly  working. 

Have  a  damper  in  the  smoke  pipe  and  keep  i't  open  only 
so  far  as  is  necessary  to  create  a  draft. 

Keep  the  water  pans  full  of  water. 

•Clean  the  furnace  and  smoke  pipe  thoroughly  in  all  parts 
at  least  once  each  year. 

Keep  the  fresh  air  duct  free  from  rubbish  and  impurities. 

Allow  plenty  of  pure  fresh  air  to  enter  the  furnace.  In 
cold  weather  part  of  this  supply  may  be  cut  off. 

Have  the  basement  well  ventilated  by  means  of  outside 
wall  ventilators,  or  by  special  ducts  leading  to  the  attic. 
Never  permit  the  basement  air  to  be  circulated  to  the  (Living 
rooms. 

To  bank  the  fires  for  the  night,  clean  the  fire,  push  the 
coals  near  the  rear  of  the  grate,  cover  with  fresh  fuel  to 
the  necessary  depth  (this  will  be  found  by  experience),  set  the 
drafts  so  they  are  nearly  closed  and  open  the  fire  doors 
slightly. 

60.  Determination  of  the  Best  Outside  Temperature  to 
Use  in  Design  and  the  •  Costs  Involved  in  Heating  by  Fur- 
naces:—As  a  basis  for  the  work  of  the  heating  and  venti- 
lating engineer  it  is  necessary  that  'he  be  well  acquainted 
with  the  temperature  conditions  in  the  locality  where  his 
services  are  employed.  He  .should  convpile  a  chart  showing 
extreme  and  average  temperatures  covering  a  period  of 
years  and  with  this  chart  a  fairly  safe  estimate  may  be 
made  upon  the  costs  involved  an  operating  any  heating 
and  ventilating  system  during  any  part  of  the  average 
'season  or  throughout  the  entire  heating  season.  Any  costs 
of  operation  arrived  at  are  only  illustrative  of  method  and 
probability,  however.  All  one  can  say  is  that  if  the  tem- 
perature in  any  one  season  averages  what  is  shown  by  the 
average  curve  for  the  period  of  years  investigated,  then 
the  cost  in  operating  the  system  may  be  easily  shown  by 


80  HEATING  AND  VENTILATION 

calculation.  Costs. in  heating  are  relative  figures  only  and 
cannot  be  predetermined  exactly  except  under  test  condi- 
tions. The  heating  engineer  should  also  know  the  mini- 
mum outside  temperatures  covering  a  period  of  years  in 
that  locality  so  as  to  determine  upon  an  outside  tempera- 
ture for  his  design  work.  Any  design  is  somewhat  of  a 
compromise  between  average  conditions  and  the  minimum 
or  extreme  conditions,  approaching  the  extreme  rather  than 
the  average.  Patrons  are  willing  that  the  heating  systems 
be  designed  so  as  to  give  normal  temperatures  in  the  rooms 
on  all  but  a  few  of  the  coldest  days.  These  minimum  con- 
ditions usually  have  a  duration  of  from  two  to  three  days 
and  it  would  not  be  considered  good  engineering  from  an 
economic  standpoint  to  design  the  system  large  enough  to 
heat  to  normal  inside  temperature  on  the  coldest  day  ex- 
perienced in  a  period  of  years.  The  plant  would  be  too 
large  and  would  require  too  much  financial  in-put.  As  an 
illustration  of  the  method  of  obtaining  the  outside  tem- 
perature to  be  used  in  design,  also  methods  of  determining 
approximate  costs  for  heating,  see  Fig.  27.  This  has  been 
worked  up  as  an  average  for  the  temperatures  of  each  of 
the  days  respectively  between  September  fifteenth  and  May 
fifteenth,  covering  a  period  of  thirty  years,  at  Lincoln, 
Nebraska.  The  minimum  temperature  curve  includes  the 
outside  temperatures  for  December  1911,  and  January  1912, 
which  may  be  regarded  as  a  period  of  unusual  severity. 
Referring  to  the  chart  it  will  be  seen  that  a  cold  period  of 
one  month  was  experienced  from  December  nineteenth  to 
January  twenty-first,  reaching  its  minimum  temperature  of 
— 26°  on  January  twelfth.  If  this  curve  were  assumed  to 
be  the  most  severe  weather  that  would  be  found  in  this 
locality,  then  by  a  study  of  conditions  one  may  easily  de- 
termine a  good  value  for  outside  temperature  in  design. 
There  were  twenty  days  when  the  temperature  was  below 
zero,  twelve  days  below  — 5°,  six  days  below  — 10°,  four 
days  below  — 15°,  two  days  below  — 20°,  and  a  part  of  one 
day  below  — 25°.  Each  of  the  extreme  and  sudden  drops 
were  such  as  to  last  from  two  to  three  days  and  were  only 
experienced  in  two  or  three  instances.  It  is  very  evident 
that  a  system  designed  for  0°  outside  would  fall  far  short 
of  the  requirement  even  when  put  under  heavy  stress.  On 
the  other  hand  one  designed  for  — 25°  outside  would  actu- 
ally come  up  to  its  capacity  for  only  a  part  of  one  day  out 


FURNACE  HEATING 


81 


of  «the  240  iheatinig  days.  One  designed  for  — 10°  would 
fulfill  conditions  without  forcing  excepting  at  two  or  three 
(periods  of  very  short  duration,  at  which  times  th.e  system 
could  ibe  forced  sufficiently  without  detriment.  The  per- 


TEMFOUTUflE  IN  OLCREES  AND  HEAT    LOS3    IN   THOUSAND  BTU 


E 


sonal  equation  enters  into  the  calculation  of  the  heat  loss 
somewhat  and  there  will  be  some  difference  of  opinion  con- 
cerning which  to  use,  — 10°  or  — 15°.  Probably  the  latter 
would  be  a  safer  value.  All  that  is  necessary  is  to  plan 


82  HEATING  AND  VENTILATION 

for  ample  service  at  all  but  one  or  two  of  the  cold  periods 
of  short  duration  and  the  system  w.ill  be  considered  very 
satisfactory  from  the  standpoint  of  size  and  capacity.  Any 
additional  amount  put  in  would  be  an  investment  of  money, 
which  is  scarcely  justified  for  the  small  percentage  of  time 
that  this  additional  capacity  would  be  called  for. 

After  the  minimum  outside  temperature  has  been  de- 
cided and  the  plant  is  designed,  one  would  like  to  know 
the  probable  expense  in  handling  such  a  plant  throughout 
the  heating  season.  Assume  an  inside  temperature  through- 
out the  building  of  70°.  Comlbine  the  two  half  months,  Sep- 
tember and  May,  into  one  month,  and  take  the  average  of 
these  average  temperatures  for  the  days  of  each  month, 
thus  giving  the  drop  in  temperature  between  the  inside 
and  the  outside  of  the  building.  The  heat  loss  from  the 
building  is  then  proportional  to  these  drops  in  tempera- 
ture. In  this  case  the  differences  are  as  follows: 

iSeptember    +   May    7°       below  70° 

October    17° 

November   32.3°         "         " 

December    44° 

January     48.7°         "         " 

February     45° 

March     34° 

April     19.5° 

Taking  the  sum  of  all  these  differences  as  the  total, 
100%,  and  dividing  each  individual  difference  by  the  total, 
we  have  the  percentages  of  loss  for  the  various  months 
as  follows: 

September  +  May 2.84%  of  total  yearly  loss 

October   6.9  %  " 

November     13.1  %  "         "  " 

December 17.8  %  "          "  " 

January     19.7  %  "          " 

February    18.2  %  " 

March    13.7  %  " 

April    7.9  %  " 

These  percentages  of  loss  indicate  what  may  be  ex- 
pected in  the  expense  for  coal  at  various  times  of  the  heat- 
ing year,  based  upon  the  average  temperatures  existing  in 
the  past  thirty  years.  From  this  the  heat  loss  has  been 


FURNACE   HEATING  83 

calculated  for  the  sample  design  stated  under  Furnace 
Heating.  The  results  are  shown  upon  the  chart  in  tons 
of  coal  per  year,  assuming  that  the  entire  house  is  heated 
to  70°  upon  the  inside  for  each  hour  between  September 
fifteenth  and  May  fifteenth.  The  lowest  curve  Is  that  for 
direct  radiation  only.  The  next  superimposed  curve  as- 
sumes fresh  air  for  ten  people.  The  third  curve  assumes 
one-half  of  the  required  air  to  be  recirculated  and  the  upper 
curve  assumes  all  the  air  to  be  fresh  air. 


84  HEATING  AND  VENTILATION 

REFERENCES. 
References  on  Furnace  Heating:. 

TECHNICAL  BOOKS. 

Snow,  Prin.  of  Heat.,  p.  27.  Snow,  Furnace  Heat.,  p.  7.  I.  C.  S. 
Prin.  of  Heat.  &  Vent.,  p.  1237.  Carpenter,  Heat.  &  Vent.  Bldga.,  p. 
310.  Hubbard,  Power,  Heat.  &  Vent.,  p.  423. 

TECHNICAL  PERIODICALS. 

Engineering  Review.  Warm  Air  Furnace  Heating,  C.  L.  Hub- 
bard,  Nov.  1909,  p.  42;  Dec.  1909,  p.  45;  Jan.  1910,  p.  66;  Feb. 
1910,  p.  48;  March  1910,  p.  51;  May  1910,  p.  48;  Aug.  1910,  p. 
29.  Warm  Air  System  of  Heating  and  Ventilating,  R.  H. 
Bradley,  May  1910,  p.  32.  Mechanical  Furnace  Heating  and 
Ventilating,  June  1910,  p.  49.  Heating  and  Vent.  System 
Installed  in  Public  School,  Fairview,  N.  J-,  July  1910,  p.  47. 
Combined  System  of  Warm  Air  and  Hot  Water  Heat,  for  a 
Residence,  Jan.  1909,  p.  26.  Warm  Air  Heating  Installation 
in  a  Brooklyn  Residence,  March  1909,  p.  38.  The  Heating  and 
Ventilating  Magazine.  Advanced  Methods  of  Warm  Air  Heat- 
ing, A.  O.  Jones,  Aug.  1904,  p.  88.  Air  Pipes,  Sizes  Required 
for  Low  Velocities,  Oct.  1905,  p.  7.  Report  of  Committee 
(A.  S.  H.  V.  E.)  to  Collect  Data  on  Furnace  Heating,  Jan. 
1906,  p.  35.  An  Improved  Application  of  Hot  Air  Heating, 
A.  O.  Jones,  July  1906,  p.  31.  The  Official  Federal  Fur- 
nace League  Method  of  Testing  Furnaces,  W.  F.  Col- 
bert, July  1910.  Domestic  Engineering.  Sanitation  in  Hot 
Air  Heating,  James  C.  Bayles,  Vol.  25,  No.  6,  Sept. 
25,  1903,  p.  261.  Trans.  A.  S.  H.  &  ~*  E.  Test  of  Hot  Air  Grav- 
ity System,  R.  C.  Carpenter,  Vol.  IX,  p.  111.  Heat  Radiators 
Using  Air  Instead  of  Water  and  Steam,  Geo.  Aylsworth,  Vol. 
IX,  p.  259.  Velocities  in  Pipes  and  Registers  in  a  Warm  Air 
System,  Vol.  XII,  p.  352.  Relative  Size  Hot  Air  Pipes,  Vol. 
XIII,  p.  270.  Velocity  of  Air  in  Ducts,  Vol.  VII,  p.  162.  The 
Metal  Worker.  Battery  of  Furnaces  with  Vent  Ducts,  Jan.  15, 
1910,  p.  85.  Air  Blast  System,  Jan.  15,  1910,  p.  93.  Origin 
and  Comparative  Cost  of  Trunk  Main  Furnace  System, 
Aug.  6,  1910,  p.  171.  Example  of  Trunk  Line  Furnace  Piping, 
April  2,  1910,  p.  463.  Furnace  System  with  Piping  50  ft.  Long, 
July  3,  1909,  p.  45.  Heat  Unit  in  Furnace  Heating,  Aug.  8, 

1908,  p.  43.     Data  on  a  Notable  School  Heating  Plant,  Nov.  6, 

1909,  p.    37.      Fan-Furnace    Residence    System,    Oct.    3,    1908, 
p.  43.     Theoretical  Construction  in  Designing  Furnace  Heat- 
ing,   Dec.    26,    1908,    p.    33.      School     Fan     Furnace     Heating 
Plant,    Oct.    8,    1910.      Combination    Heating    in    Cold    Terri- 
tory,   Sept.    29,    1911.      Underwriters'    Tests    of    Wall    Stacks, 
July   1,    1911.     Design   of  Fan  Blast  Heating,   H.   C.   Russell, 
Jan.  21,  1911;  Feb.  25.  1911. 


CHAPTER   VI. 


HOT  WATER  AND  STEAM  HEATING. 


DESCRIPTION  AND   CLASSIFICATION   OF  THE   SYSTEMS. 

01.  Hot  Water  and  Steam  Systems  Compared  to  Fur- 
nace Systems: — As  compared  to  the  warm  air  or  furnace 
plant,  the  hot  water  and  the  steam  installations  are  more 
complicated  in  the  number  of  parts;  they  use  a  more  cum- 
bersome heat  carrying-  medium,  for  which  a  return  path  to 
the  boiler  must  be  provided;  and  have  parts,  in  the  form 
of  radiators,  which  occupy  valuable  room  space.  But  the 
steam  and  hot  water  plants  have  the  advantage  in  that 
their  circulations,  and  hence  their  transference  of  heat, 
are  quite  positive,  and  not  affected  by  wind  pressures.  A 
hot  water  or  a  steam  system  will  carry  heat  just  as  readily 
to  the  windward  side  of  a  house  as  it  will  to  the  leeward 
side,  a  point  which,  with  a  furnace  installation,  is  known 
to  be  quite  impossible.  Furnace  heating,  on  the  other  hand, 
has  the  advantage  of  inherent  ventilation,  while  the  hot 
water  and  steam  systems,  as  usually  installed,  provide  no 
ventilation  except  that  due  to  air  leakage. 

62.     The  Parts  of  Hot  Water  and  Steam  Systems: — A  hot 

water  or  a  steam  system  may  be  said  to  consist  of  three 
principal  parts:  first,  the  boiler  or  heat  generator;  second, 
the  radiators  or  heat  distributors;  and  third,  the  connecting 
pipe-lines,  which  provide  the  circuit  paths  for  the  hot  water 
or  the  stea*m.  In  the  hot  water  system  it  is  essential  that 
the  heat  generator  be  located  at  the  lowest  point  in  the 
circuit,  for,  as  was  explained  in  Art.  5,  the  only  motive 
force  is  that  due  to  the  convection  of  the  water.  In  the 
steam  system  this  is  not  essential,  as  the  pressure  of  the 
steam  forces  it  outward  to  the  farthest  points  of  the  system. 
The  water  of  condensation  may  or  may  not  be  returned  by 
gravity  to  the  boiler.  Hence,  with  a  steam  system  a  radiator 
may  be  placed  below  the  boiler,  if  its  condensation  be  trapped 
or  otherwise  taken  care  of. 


86  HEATING  AND  VENTILATION 

63.  Definitions: — In  speaking  of  the  piping  of  heating 
installations,  several  terms,  commonly  used  by  heating  en- 
gineers, should  be  thoroughly  understood.  The  large  pipes 
in  the  basement  connected  directly  to  the  source  of  heat, 
and  serving  as  feeders  or  distributors  of  the  heating  me- 
dium to  the  pipes  running  vertically  in  the  building,  are 
known  as  mains.  The  flow  mains  are  those  carrying  steam 


Fig.   28. 


Pig.  29. 


or  hot  water  from  the  source  of  heat  towards  the  radiators, 
and  the  return  mains  are  those  carrying  water  or 
condensation  from  the  radiators  to  the  source  of 
heat.  Those  vertical  pipes  in  a  building  to  which 
the  radiators  are  directly  connected  are  called  risers, 
while  the  short  horizontal  pipes  from  risers  to  radi- 
ators are  usually  termed  riser  arms.  As  there  are  flow 
mains  and  return  mains,  so  also,  there  are  flow  risers  and 
return  risers.  A  radiator  should  have  at  least  two  tappings, 
one  below  for  the  entry  of  the  heating  medium,  and  one 
on  the  end  section  opposite,  near  the  top  for  air  discharge 
as  shown  by  the  connected  steam  radiator  of  Pig.  28.  It 
may  have  three,  a  flow  tapping  and  a  return  tapping  at  the 
bottom  of  the  two  end  sections,  and  the  third  or  air  tapping 
near  the  top  of  the  end  section  at  the  return  end  as  shown 
by  the  connected  hot  water  radiator  of  Fig.  29.  A  return 


HOT    WATER   AND   STEAM   HEATING 


87 


main  traversing  the  basement  above  the  water  line  of  the 
boiler  is  designated  as  a  dry  return  and  carries  both  steam 
and  water  of  condensation;  one  in  such  position  below  the 
water  line  as  to  be  filled  with  water  is  designated  a  wet 
return,  and  the  returns  of  all  two-pipe  radiators  connecting 
with  wet  returns  are  .said  to  be  sealed. 

64.  Classification: — One  classification  of  hot  water  and 
steam  systems  is  based  upon  the  position,  and  manner  in 
which  the  radiators  are  used.  The  system  which  is,  per- 
haps, most  familiar  is  the  one  wherein  radiators  are  placed 
directly  within  the  space  to  be  heated.  This  heating  is  ac- 


Fig.    30. 


Fig.    31. 


complished  by  direct  radiation  and  by  air  convection  cur- 
rents through  the  radiators,  no  provision  being  made  for  a 
change  of  air  in  the  room.  This  is  known  as  the  direct 
system,  and,  while  it  causes  movements  of  the  air  in  the 
room»  it  produces,  no  real  ventilation.  See  Fig.  30. 

Is.  the  direct-indirect  system,  the  radiator  is  also 
placed-within  the  space  or  room  to  be  heated,  but  its  lower 
half  is  so  encased  and  connected  to  the  outside  of  the  build- 


HEATING  AND  VENTILATION 


ing-  that  fresh  air  is  continually  drawn  up  through  the 
radiator,  is  heated,  and  thrown  out  into  the  room  as  shown 
by  Fig.  31.  Thus  is  established  a  ventilating1  system  more 
or  less  effective. 

In  the  purely  indirect  system,  Pig.  32,  the  radiating  sur- 
face is  erected  somewhere  remote  from  the  rooms  to  be 
heated,  and  ducts  carry  the  heated  air  from  the  radiator 
to  the  rooms  either  by  natural  convection,  as  in  some  in- 
stallations, or  by  fan  or  blower  pressure,  as  in  others. 
When  all  the  radiation  for  an  entire  building  is  installed 


Fig.  32. 

together  in  one  basement  room,  and  each  room  of  the  build- 
ing has  carried  to  it,  its  share  of  heat  by  forced  air  through 
ducts  from  one  large  centralized  fan  or  blower,  the  system 
is  called  a  Plenum  System,  and  is  given  special  consideration 
in  Chapters  X  to  XII. 

65.  A  second  classification  of  steam  and  hot  water  sys- 
tems is  made  according  to  the  method  of  pipe  connection 
between  the  heat  generator  and  the  radiation.  That  known 
as  the  one-pipe  system,  Fig.  33,  is  the  simplest  in  construc- 
tion and  is  preferred  by  many  for  the  steam  installations. 
As  the  name  indicates,  its  distinguishing  feature  is  the 
single  pipe  leading  from  the  source  of  heat  to  the  radiator, 
the  steam  and  the  returning  condensation  both  using  this 
path.  In  the  risers  and  connections,  the  steam  and  con- 
densation flow  in  opposite  directions,  thus  requiring  larger 
pipes  than  where  a  flow  and  a  return  are  both  provided. 
In  this  system  the  condensation  usually  flows  with  the 
steam  in  the  main,  and  not  against  it,  until  it  reaches  such 
a  point  that  it  may  be  dripped  to  a  separate  return 
and  then  led  to  the  boiler.  In  >the  so-called  one-pipe 
hot  water  system,  radiators  have  two  tappings  and  two 


HOT    WATER    AND    STEAM    HEATIXG 


Fig.   33. 

risers,  but  the  flow  riser  is  tapped  out  of  the  top  of  the 
single  basement  main,  while  the  return  riser  is  tapped  into 
the  bottom  of  that  same  main  by  either  of  the  special  fit- 
tings shown  in  section  in  Fig.  34.  The  theory  is  that  the 
hot  water  from  the  boiler  travels 
along  the  top  of  the  horizontal  base- 
ment main,  while  the  cooler  water  from 
the  radiators  travels  along  the  bottom 
of  this  same  main.  Hence  the  neces- 
sity for  tapping  flow  risers  out  of  the 
top  and  return  risers  into  the  bottom 
of  this  main,  thus  avoiding  a  mixing 
of  the  two  streams.  Where  mains  are 
short  and  straight  as  in  the  smaller 
Pig.  34.  residence  installations,  this  system 


90 


HEATING  AND  VENTILATION 


seems  to  give  satisfaction;  but  it  is  very  evident  that,  where 
basement  mains  are  long  and  more  complicated,  a  mixing 
©f  the  two  streams  is  unavoidable,  thus  rendering  the  sys- 
tem unreliable. 

The  two-pipe  system  is  used  on  both  steam  and  hot 
water  installations.  For  steam  work  it  is  probably  no 
better  than  the  one-pipe  system  but  for  hot  water  work  it 
is  much  preferred.  In  this  system  two  separate  and  dis- 
tinct paths  may  be  traced  from  any  radiator  to  the  source 
of  heat.  In  the  basement  are  two  mains,  the  flow  and  the 
return,  and  the  risers  from  these  are  always  run  in  pairs, 
the  flow  riser  on  one  side  of  a  tier  of  radiators,  the  return 
riser  on  the  other  side.  A  two-pipe  steam  system  must 
have  a  sealed  return.  Typical  two-pipe  main  and  riser  con- 
nections are  shown  in  Fig.  35. 


Fig.    35. 


Fig.    36. 


66.  A  third  system,  known  as  the  attic  main,  or  Mills 
system,  has  found  much  favor  with  heating  engineers  in 
the  installation  of  the  larger  steam  plants  although  it  could 
be  applied  as  well  to  the  larger  hot  water  plants.  The 
distinguishing  feature,  when  applied  to  a  steam  system, 
is  the  double  main  and  single  riser,  so  arranged  that  the 
condensation  and  live  steam  flow  in  the  same  direction. 


HOT   WATER   AND    STEAM   HEATING  91 

This  is  accomplished  by  taking  the  live  steam  directly  to 
the  attic  by  one  large  main,  which  there  branches,  as  need 
be,  to  supply  the  various  risers,  only  one  riser  being  used 
for  each  tier  of  radiators  and  the  direction  of  flow  of  both 
steam  and  condensation  in  risers  being  downward.  Hence, 
this  system  avoids  the  unsightliness  of  duplicate  risers,  as 
in  the  two-pipe  system,  and  avoids  the  disadvantage  of  the 
one-pipe  basement  system,  the  last  named  having  steam 
and  condensation  flowing  in  opposite  directions  in  the  same 
pipe.  Fig.  36  shows  two  common  methods  of  connecting 
risers  and  radiators  with  this  system. 

67.     Diagrams  for  Steam  and  Hot  Water  Piping  Systems: 

— .Figs.  37  to  43  inclusive  show  somie  of  the  methods  for 
connecting  up  piping  systems  between  the  source  of  heat 
and  the  radiators.  At  the  radiators  A,  B,  C  and  D  are  shown 
different  methods  of  connecting  between  the  radiators  and 
mains.  In  every  case  the  various  forms  of  branches  below 
the  floor  and  behind  the  radiators  are  for  the  purpose  of 
taking  up  the  expansion.  It  will  be  noticed  that  the  two- 
pipe  steam  systems  have  sealed  returns  where  they  enter 
the  main  return  above  the  water  line  of  the  boiler. 

In  some  steam  systems  where  atmospheric  pressure  is 
maintained,  special  valves  with  graduated  control  admit  steam 
to  the  upper  part  of  the  radiator.  The  returns  enter  into  a 
receiver  near  the  boiler  with  a  vapor  and  air  relief  to  the 
atmosphere  through  some  form  of  condenser,  having  an  out- 
let pipe  leading  to  an  air  shaft  or  to  a  chimney.  The  pres- 
sure upon  this  return  is  maintained  in  such  a  case  approx- 
imately 14.7  pounds.  The  water  type  of  radiator  is  used, 
having  the  sections  connected  both  top  and  bottom  and  with 
this  graduated  control  only  that  amount  of  radiation  which 
is  necessary  to  heat  the  room  on  a  given  day  is  employed. 
Such  a  system  is  economical,  safe  and  can  be  operated  In 
connection  with  any  bind  of  radiation.  I  ig.  43  is  typical  of 
such  systems. 


HEATING  AND  VENTILATION 


ONE    PIPE  STEAM    SYSTEM -BASEMENT     MAIN 


Fig,    37. 


TWO    PIPE   STEAM    SYSTEM-BASEMENT    MAIN 


Fig.  38. 


HOT    WATER    AND    STEAM   HEATING  93 


Fig.   39, 


ONE    PIPE.  'SYSTEM-HOT   WATER 


Fig-.    40. 


HEATING  AND  VENTILATION 


TWO    PIPL    SYSTEM    HOT  WATER -BASEMENT     MAIN 


Fig.   41. 


|U TO   EXPANSION   TANK 


Fig1.  42. 


HOT    WATER    AND    STEAM   HEATING  95 

VAPOR   SYSTEM  OF  STEAM  HEATINO 


Fig-.    43. 

68.  Accelerated  Hot  Water  Heating  Systems: — Improve- 
ments have  been  devised  for  hot  water  heating  whereby  the 
circulation  of  the  water  is  increased  .above  that  obtained  by 
the  open  tank  system.  By  increasing-  the  velocity  of  the 
water,  pipe  sizes  may  be  reduced,  resulting  in  an  economy 
in  the  cost  of  pipe  and  fittings.  In  addition  to  this,  where 
the  temperature  of  the  water  is  carried  above  that  due  to 
atmospheric  pressure,  the  radiation  may  theoretically  be 
reduced  below  that  for  the  open  tank  system.  How  far 
these  economies  may  be  pursued  in  designing  is  a  question 
which  should  be  very  carefully  considered.  In  many  cases 
the  amount  of  radiation  is  kept  the  same  and  the  chief  dif- 
ference merely  that  of  pipe  sizes.  This  article  is  descriptive 
of  several  of  the  types  of  accelerated  systems  in  use  and  is 
not  intended  as  a  critical  analysis  of  the  merits  of  any  one 
as  compared  to  the  others. 

Of  all  the  principles  employed  for  accelerating  the  cir- 
culating water,  four  will  be  mentioned.  First,  by  increas- 
ing the  pressure  of  the  open  tank  system  thus  raising  the 
temperature  above  212  degrees.  Second,  by  superheating  a 
part  or  all  of  the  circulating  water  as  it  passes  through  the 
heater  and  condensing  the  steam  thus  formed  by  mixing  it 


96 


HEATING  AND  VENTILATION 


with  a  portion  of  the  cold  circulating  water  of  the  return. 
Third,  by  introducing  steam  or  air  into  the  main  riser  pipe 
near  the  top  of  the  system.  Fourth,  by  mechanically  oper- 
ated pumps  or  motors. 

Descriptive  of  the  first  principle,  Fig.  44  shows  a  mer- 
cury-seal   tube   connected    between    the    upper   point    of   the 
^  main    riser    and    the    expansion    tank.      This    is 

designed  to  hold  a  pressure  of  about  10  pounds 
gage,  the  water  from  the  system  filling  the 
casement  and  pressing  down  upon  the  top 
of  the  mercury  in  the  bowl.  Increasing  the 
pressure  in  the  system  lowers  the  level  of  the 
mercury  in  the  bowl  and  forces  the  mercury 
up  the  central  tube  A  until  the  differential 
pressure  is  neutralized  by  the  static  head  of 
the  mercury.  If  the  pressure  becomes  great 
enough  to  drop  the  level  of  the  mercury  to 
the  tube  entrance,  water  and  steam  will  force 
through  the  mercury  to  chamber  D  and  from 
thence  through  the  expansion  tank  to  the  over- 
flow. Any  mercury  forced  out  of  the  tube  A 
by  the  velocity  of  the  water  and  steam,  strikes 
the  deflecting  plate  0  and  drops  back  through 
the  annular  opening  B  to  the  mercury  bulb 
below.  As  the  pressure  is  reduced  in  the 
system  the  mercury  drops  in  tube  A  to  the 
level  of  that  in  the  bulb  and  water  from  the 
expansion  tank  passes  down  through  the 
mercury-seal  into  the  heating  system  to  replace  any  that 
has  been  forced  out  to  the  expansion  tank.  This  action  is 
automatic  and  is  controlled  entirely  by  the  pressure  within 
the  system.  The  only  loss,  if  any,  is  -that  amount  wihich 
goes  out  the  overflow.  The  above  represents  essentially 
what  is  known  as  the  Honeywell  System  of  .acceleration. 
A  modification  of  the  above  is  used  in  the  Cripps  System. 
In  this  the  mercury-seal  is  placed  beyond  -the  expansion 
tank  and  puts  the  expansion  tank  under  pressure. 

The  second  principle  is  illustrated  by  Figs.  45  and  46. 
Fig.  45,  known  as  the  Koerting  System,  has  a  series  of 
motor  pipes  leading  from  the  upper  part  of  the  heater  to  a 
mixer,  where  the  steam  is  condensed  before  it  reaches  the 


Fig.    44 


HOT    WATER    AND    STEAM   HEATING 


97 


expansion  tank  by  the  water  entering  through  the  by-pass 
from  the  return.  The  velocity  of  the  steam  and  water 
through  the  motor  pipes  and  the  partial  vacuum  caused  by 
the  condensation  in  the  mixer  produces  the  acceleration  up 
the  flow  pipe. 


Fig.    46. 

In  the  Jorgensen  and  Bruchner  Systems  the  heater  K 
delivers  the  hot  water  up  the  flow  pipe  to  a  regulator  R, 
where  a  separation  takes  place  between  the  steam  particles 
and  the  water,  .thus  causing  an  acceleration  up  the  motor 
pipe  to  the  expansion  tank  A.  The  water  in  the  flow  pipe  2 
is  probably  near  to  the  temperature  of  that  in  1.  After 
passing  through  the  radiators  the  water  in  3  is  at  a  lower 
temperature  than  that  in  2.  The  steam  particles  which 
have  collected  in  the  expansion  tank  A  above  the  water  line 
•are  condensed  in  V.  The  acceleration  in  the  system  is  thug 
produced  by  a  combination  of  the  upward  movement  of  the 
steam  particles  in  motor  pipe  1  and  the  induced  upward 
current  in  3  toward  the  condenser  V.  It  will  be  noticed 
in  the  figures  that  the  condensation  in  one  system  takes 
place  before  the  expansion  tank  a.nd  in  the  other  system  after 


98 


HEATIXG  AND   VJKNTl.LuA.TiOW 


it  has  passed  the  expansion  tank.  Each  of  the  systems  illus- 
trated may  be  carried  under  pressure  by  a  safety  valve  as 
at  B  or  by  an  expansion  tank  located  high  enough  to  give 
sufficient  static  head. 

The  third  principle  is  well  shown  by  what  is  known  as 
the  Reck  System.  Fig.  47  is  a  diagrammatic  view  and  Fig. 
48  a  detail  of  the  accelerating  part  of  the  system.  The 


DETAIL    OF    A.S.AND  C. 

Fig.    48. 


water  passes  directly  from  the  heater  up  the  main  riser 
where  it  enters  the  condenser  C  and  thence  into  the  expan- 
sion tank  A  as  a  supply  to  the'  flow  pipes  of  the  system. 
Steam  from  a  separate  boiler  is  admitted  to  the  mixer  B 
above  the  condenser  and  enters  the  circulating  water  just 
below  the  expansion  tank.  The  velocity  of  the  steam  and 
the  partial  vacuum  caused  by  the  condensation  induces  a 
current  up  the  flow  pipe  to  the  expansion  tank.  Wihen  the 
water  level  in  the  expansion  tank  reaches  the  top  of  the 
overflow  pipe  the  water  returns  to  the  steam  boiler  through 
the  condenser  C  where  it  gives  off  heat  to  the  upper  cur- 
rent of  the  circulating  water.  It  will  be  seen  that  the 


HOT    WATER  AND   STEAM   HEATING 


water  In  the  system  and  the  steam  from  the  boiler  unite 
from  the  inlet  at  the  mixer  to  the  expansion  tank.  On  all 
other  parts  of  the  systems  they  are  independent. 

Fig.  49  is  a  modification  of  this  same  principle,  wherein 
air  is  injected  in  the  riser  pipe  at  B  and  causes  the  acceler- 
ation by  a  combination  of  the  par- 
tial vacuum  produced  by  the  steam 
condensation  as  just  mentioned  and 
the  upward  current  of  the  air  par- 
ticles as  in  an  air  lift.  Steam  enters 
through  the  pipe  J  and  ejector  H  to 
the  mixer  at  B  where  it  is  con- 
densed. In  passing  through  H  airFLOW 
is  drawn  from  the  tank  E  and  en- 
ters the  main  riser  with  the  steam. 
The  upward  movement  of  this  air 
through  the  motor  pipe  to  the  tank 
induces  an  upward  flow  of  the  water 
in  the  main  riser.  By  this  combina- 
tion there  are  formed  three  com- 
plete circuits,  water,  steam  and  air, 
uniting  as  one  circuit  from  the  mix- 
er B  to  the  expansion  tank  E.  The  Fig.  49. 
steam  furnished  in  principle  3  may  be  supplied  by  a  separate 
steam  boiler  or  by  steam  coils  in  the  fire  box  of  a  hot  water 
boiler. 

In  the  fourth  principle  the  acceleration  is  produced  by 
some  piece  of  mechanism  as  a  pump  or  motor  placed  direct- 
ly in  the  circuit.  This  principle  is  discussed  under  District 
Heating  and  will  be  omitted  here. 

69.  Vacuum  Systems  for  Steam: — Most  commonly,  the 
systems  mentioned,  when  steam,  are  installed  as  the  so- 
called  low  pressure  systems,  which  term  indicates  an  abso- 
lute pressure  of  about  18  pounds  per  square  inch  or  3% 
pounds  gage  pressure.  On  extensive  work,  it  has  been 
found  advantageous  to  install  a  vacuum  system  to  increase 
•economy,  also  to  insure  positive  steam  circulation  by  prompt 
removal  of  condensation  through  vacuum  returns.  Even 
for  comparatively  small  residence  installations  vacuum  ap- 
plications of  various  kinds  are  becoming  common. 

Vacuum  systems  may  be  divided  into  two  classes,  ac- 
cording to  the  way  in  which  the  vacuum  is  maintained.  For 


100 


HEATING  AND  VENTILATION 


comparatively  small  plants,  not  using  exhaust  steam,  the 
vacuum  is  maintained  by  mercury  seal  connections,  and 
these  plants  are  usually  referred  to  as  mercury  seal  vacuum 
systems.  These  mercury  seals  may  be  attached  to  any 
standard  one  or  two-pipe  system  by  merely  replacing  the 
ordinary  air  valve  by  a  special  connection,  which  in  real- 
ity is  only  a  barometer.  An  iron  tube,  Fig.  50,  dips  just 
below  the  surface  of  the  mercury  in  the  well  on  the  floor 
and  extends  vertically  to  the  radiator  air  tap- 
ping to  which  the  tube  connects  by  a  fitting 
1  which  will  allow  air  to  pass  into  and  through 
the  barometer,  but  will  not  allow  steam  to 
pass.  When  the  system  is  first  fired  up  and 
steam  is  raised  to  several  pounds  gage,  the  air 
leaves  all  the  radiators  by  bubbling  through 
the  mercury  seal  at  the  end  of  the  vertical 
iron  tube.  If  the  fire  is  then  allowed  to  go  out, 
the  steam  will  condense,  and  produce  an  almost 
perfect  vacuum  in  the  entire  system,  provided 
all  pipe  fitting  has  been  carefully  done.  This 
system  may  be  operated  as  a  vacuum  system 
at  4  or  5  pounds  absolute  pressure  and  have 
the  water  boiling  as  low  as  150  to  160  degrees. 
The  flexibility  of  this  system  recommends  it 
highly.  Applied  to  a  residence  or  store,  the 
plant  may  be  operated  during  the  day  at  sev- 
eral pounds,  gage  pressure,  if  necessary,  but 
when  fires  are  banked  for  the  night,  steam  re- 
mains in  all  pipes  and  radiators  as  long  as  the 
temperature  of  the  water  does  not  fall  much 
below  150  degrees.  This  is  in  sharp  contrast 
with  the  ordinary  system,  where  steam  disap- 
pears from  all  radiators  as  soon  as  the  water 
temperature  drops  below  212  degrees.  The 
promptness  with  which  heat  may  be  obtained  in  the  morn- 
ing is  noteworthy,  for,  if  the  vacuum  has  been  maintained, 
steam  will  begin  to  circulate  as  soon  as  the  water  has  been 
raised  to  about  150  degrees.  According  to  demands  of  the 
weather,  the  radiators  may  be  kept  at  any  temperature 
along  the  range  of  150  to  220  degrees,  thus  giving  great 
flexibility. 


Fig.    50. 


HOT    WATER   AND   STE.iK  '.  HfiA^TlNG  101 

Instead  of  having1  a  barometric  tube  at  each  radiator, 
one  mercury  seal  may  be  supplied  in  the  basement,  and  the 
air  tappings  of  all  radiators  connected  to  the  top  of  the 
tube  iby  %  inch  piping1.  In  practice  it  is  found  very  difficult 
to  obtain  a  system  of  piiping  sufficiently  tight  to  maintain 
a  :hig;h  vacuum  Oin  the  mercury  seal  system. 

The  second  class  of  vacuum  systems  includes  those 
designed  especially  for  use  in  office  buildings,  and  where- 
in the  vacuum  is  maintained  by  an  aspirator,  exhauster  or 
pump  of  some  description.  This  exhauster  may  handle  only 


Fig.  51. 


Fig.  52. 


the  air  of  the  system,  that  is,  it  may  be  connected  only 
to  the  air  tappings  of  all  radiators,  as  in  the  Paul  system, 
Fig.  51,  or  the  exhauster  may  handle  both  air  and  con- 
densation and  be  connected  to  the  return  tappings  of  all 
radiators,  as  in  the  Webster  system,  Fig.  52.  The  Paul 
system  is  fundamentally  a  one-pipe  system,  using  exhaust 
or  live  steam  and  maintaining  its  circulation  without  back 
pressure,  by  exhausting-  each  radiator  at  its  air  tapping, 
and  also  exhausting  the  condensation  from  the  basement 
tank  in  which  it  has  been  collected  by  gravity.  For  an 


102  HEATING  AND  VENTILATION 

aspirator  this  system  uses  either  air,  steam,  or  hot  water, 
as  the  conditions  may  determine.  The  Webster  system  is 
fundamentally  a  two-pipe  system  and  exhausts  from  the 
radiators  both  the  air  and  water  of  condensation,  all  radi- 
ator returns  being  connected  to  the  (usually)  steam  driven 
vacuum  pump.  These  systems  are  designed  to  use  both  exhaust 
and  live  steam,  and  hence  are  finding  wide  application  in  the 
modern  heating  of  manufacturing  plants.  See  also  Chapter 
IX 


CHAPTER  VII. 


HOT  WATER  AND  STEAM  HEATING. 


RADIATORS,     BOILERS,     FITTINGS     AND     APPLIANCES- 

The  various  systems  just  described  are  merely  different 
ways  of  connecting  the  source  of  heat  to  the  distributors 
of  heat,  i.  e.,  methods  of  pipe  connections  between  heater 
and  radiators.  Many  forms  of  radiators  exist,  as  well  as 
many  types  of  heaters  and  boilers,  each  adapted  to  its  own 
peculiar  condition.  It  is  in  this  choice  of  the  best  adapted 
material  that  the  heating  engineer  shows  the  degree  of 
his  practical  training,  and  the  closeness  with  which  he  fol- 
lows the  latest  inventions,  improvements  and  applications. 

70.  Classification  as  to  Material: — Radiators  may  be 
classified,  according  to  material,  as  cast  iron  radiators, 
pressed  steel  radiators  and  pipe  coil  radiators.  Cast  radi- 
ators have  the  hollow  sections  cast*  as  one  piece,  of  iron. 
The  wall  is  usually  about  %  inch  to  %  inch  thick,  and  is 
finally  tested  to  a  pressure  of  100  pounds  per  square  inch, 
Sections  are  joined  by  wrought  iron  or  malleable  nipples 
which,  at  the  same  time,  serve  to  make  passageways  be- 
tween any  one  section  and  its  neighbors  for  the  current  of 
heating  medium,  whether  of  steam  or  hot  water.  Cast  iron 
radiators  have  the  disadvantage  of  heavy  weight,  danger 
of  breaking  by  freezing,  occupying  much  space,  and  having 
a  comparatively  large  internal  volume,  averaging  a  pint  and 
a  half  per  square  foot  of  surface. 

Pressed  radiators  are  made  of  sheet  steel  of  No.  16 
gage,  and,  after  assembly,  are  galvanized  both  inside  and 
out.  Each  section  is  composed  of  two  pressed  sheets  that 
are  joined  together  by  a  double  seam  as  shown  at  a,  Fig. 
53,  which  illustrates  a  section  through  a  two-column  unit. 


Fig.   53. 

The  Joints  between  the  sections  or  units  are  of  the  same 
kind.  It  is  readily  seen  that  such  construction  tends  to- 
ward a  very  compact  radiating  surface.  Pressed  radia- 


.1,0-?  HEATING  AND  VENTILATION 

tors  are  comparatively  new,  but,  in  their  development, 
promise  much  in  the  way  of  a  light,  compact  radiation.  In 
comparison  with  the  cast  iron  radiators,  they  are  free  from 
the  sand  and  dirt  on  the  inside,  thus  causing  less  trouble 
with  valves  .and  traps.  The  internal  volume  will  approxi- 
mate one  pint  per  square  foot  of  surface.  See  Fig.  54. 

Radiators  composed  of  pipes,  in  various  forms,  are 
commonly  referred  to  as  coil  radiators.  They  are  daily 
becoming  less  common  for  direct  and  direct-indirect  work, 
because  of  their  extreme  unsightliness.  Piping  is  still 
much  used  as  the  heat  radiator  in  indirect  and  plenum 
systems,  although  both  cast  and  pressed  radiators  are  now 
designed  for  both  of  these  purposes  where  low  pressure 
st^am  is  used.  In  all  coil  radiator  work,  no  matter  for 
what  purpose,  1  inch  pipe  is  the  standard  size.  However, 
in  some  cases  pipes  are  used  as  large  as  2  inches  in  diam- 
eter. Standard  1  inch  pipe  is  rated  at  1  square  foot  of  heat- 
ing surface  per  3  lineal  feet  and  has  about  1  pint  of  con- 
taining capacity  per  square  foot  of  surface. 

71.  Classification  as  to  Form: — Radiators  may  again  be 
classified  in  accordance  with  form,  into  the  one,  two,  three, 
and  four-column  floor  types,  the  wall  type,  and  the  flue 
type.  See  Fig.  54.  These  terms  refer  only  to  cast  and 
pressed  radiators.  By  the  column  of  a  radiator  is  meant 
one  of  the  unit  fluid-containing  elements  of  which  a  sec- 
tion is  composed.  When  the  section  has  only  one  part  or 
vertical  division,  it  is  called  a  single-column  or  one-column 
type;  when  there  are  two  such  divisions,  a  two-column; 
when  three,  a  three-column;  and  when  four,  a  four- 
column  type.  What  is  known  as  the  wall  type  radiator  is 
a  cast  section  one-column  type  so  designed  as  to  be  of 
the  least  practicable  thickness.  It  presents  the  appear- 
ance, often,  of  a  heavy  grating,  and  is  so  made  as  to 
have  from  5  to  9  square  feet  of  surface,  according  to  the 
size  of  the  section.  One-column  floor  radiators  made  with- 
out feet  are  often  used  as  wall  radiators.  A  flue  radiator 
is  a  very  broad  type  of  the  one-column  radiator,  the  parts 
being  so  designed  that  the  air  entering  between  the  sections 
at  the  base  is  compelled  to  travel  to  the  top  of  the  sections 
before  leaving  the  radiator.  This  type  is  therefore  well 
adapted  to  direct-indirect  work.  See  Fig.  54. 


HOT    WATER    AND    STEAM    HEATING 


105 


Stairway  Type    Dining  Room  Type    Flue  Type    Circular  Type 


CAST     RADIATORS 


Wall  Type 


Two-Column 
Type 


Three-Column 
Type 


Pour-Column 
Type 


PRESSED     RADIATORS 


Single-Column     Two-Column 
Type  Type 


Three-Column 
Type 


Wall  Type 


Fig.   54. 


106  HEATING  AND  VENTILATION 

Many  special  shapes  of  assembled  radiators  will  be 
met  with,  but  they  will  always  be  of  some  one  of  the  fun- 
damental types  mentioned  above.  For  instance,  there  are 
"stairway  radiators,"  built  up  of  successive  heights  of 
sections,  so  as  to  fit  along  the  triangular  shaped  wall  under 
stairways;  there  are  "pantry"  radiators  built  up  of  sections 
so  as  to  form  a  tier  of  heated  s.helves;  there  are  "dining 
room"  radiators  with  an  oven-like  arrangement  built  into 
their  center;  and  there  are  "window  radiators"  built  with 
low  sections  in  the  middle  and  higher  ones  at  either  end, 
so  as  to  fit  neatly  around  a  low  window.  Fig.  54  shows  a 
number  of  these  common  forms  as  used  in  practice. 

72.  Classification  as  to  Heating  Medium: — A  third  class- 
ification   of    radiators,    according    to    heating    medium    em- 
ployed,   gives    rise     to     the     terms     steam    radiator    and     hot 
water  radiator.      Casually,    one    would   notice   little   difference 
between  the  two,  but  in  construction  there  is  a  vital  differ- 
ence.     Steam    radiation   has    the    sections   joined   by   nipples 
along   the    bottom   only,    but   hot   water   radiation   has    them 
joined  along  the  top  as  well.     This  is  quite  essential  to  the 
proper  circulation  of  the  water.     Steam  radiation  is  always 
tapped  for  pipe  connections  at  the  bottom.     Hot  water  rad- 
iation may  have   the   flow  connection  enter  at  the   top,   and 
the    return    connection    leave   at   the    bottom,    or    may    have 
both   connections   at  the   bottom.     Hot  water   radiation   can 
b      heated  very    successfully   with   steam,   but   steam    radia- 
tion cannot  be  used  with   hot   water. 

73.  High   versus   Low   Radiators: — In   the   adoption    of  a 
radiator  height,  the  governing  feature  is  usually  the  space 
allowed  for  the  radiator.     Thus,   if  a  radiator  of  26   inches 
in  height  requires  so  many  sections  as  to  become  too  long, 
then  a  32  inch  or  a  38  inch  section  may  be  taken.     In  gen- 
eral,   however,    low    radiators    should    be    used    as    far    as 
possible,  for,  with  a  high  radiator,  the  air  passing  up  along 
the  sides  of  the  sections  becomes  heated  before  reaching  the 
top,  and   therefore   receives  less   heat   from    the   upper   half 
of    the    radiator,    since    the    temperature    difference    here    is 
small.      Hence,   the   statement    that  low   radiators  are   more 
efficient,    that    is,    will    transmit   more    B.    t.    u.    per   square 
foot  per  hour  than  will  the  high   radiators. 

The  amount  of  heat  that  will  be  transmitted  through  a 
radiator  to  a  room  is  controlled  also  by  the  width  of  the 


HOT   WATER   AND   STEAM   HEATING  107 

radiator,  narrow  radiators  being-  more  efficient  than  wide 
ones.  Considering  both  height  and  number  of  columns  the 
rate  of  transmission,  used  in  formulas  30  and  31  as  1.7,  would 
change  to: 

1   column  radiator,   30"  high   1.8   B.   t.   u. 
2  and  3          "  "  30"       "      1.7 

4          "  "  30"        "       1.6 

For  high  and  low  radiators  this  may  be  reduced  or  increased 
ten  per  cent,  respectively  for  a  48  inch  and  a  16  inch  radiator. 

74.       Effect    of    Condition    of    Radiator    Surface    on    the 

Transmission  of  Heat: — The  efficiency  of  a  radiator  depends 
very  largely  upon  the  condition  of  its  outer  surface,  a 
rough  surface  giving  off  very  much  more  heat  than  a 
smooth  surface.  Painting,  (bronzing,  shellacing  or  cover- 
ing the  radiator  .in  any  manner  affects  the  ability  of  the 
radiator  to  impart  heat  to  the  air  circulating  around  it. 
Various  tests  bearing  upon  this  question  have  been  con- 
ducted, agreeing  fairly  well  in  general  results.  A  series 
of  tests  .conducted  by  Prof.  Allen  at  the  University  of 
Michigan,  indicated  that  the  ordinary  bronzes  of  copper, 
zinc  or  aluminum  caused  a  reduction  in  the  efficiency  below 
that  of  the  ordinary  rough  surface  of  the  radiator  of 
about  25  per  cent.,  while  white  zinc  paint  and  white  enamel 
gave  the  greatest  efficiency,  being  slightly  above  that  of 
the  original!  surface  Numerous  coats  of  paint,  even  as  high 
as  twelve,  seemed  to  affect  the  efficiency  in  no  appreciable 
manner,  it  being  the  last  or  outer  coat  that  always  de- 
termined at  what  rate  the  radiator  would  transmit  its  heat. 

75.    Amount  of  Surface  Presented  by  Various  Radiators: — 

Table  X,  gives,  according  to  the  columns  and  heights, 
the  number  of  square  feet  of  heating  surface  per  section 
in  cast  and  pressed  radiators.  This  table  will  be  found  to 
present,  in  very  compact  form,  the  similar  and  much  more 
extended  tables  in  the  various  manufacturers'  catalogs. 
An  approximate  rule  supplementing  this  table  and  giving, 
'  to  a  very  fair  degree  of  accuracy,  the  square  feet  of  sur- 
face in  any  standard  radiator  section,  is  as  follows:  mul- 
tiply the  height  of  the  section  in  inches  "by  the  number  of  columns 
and  divide  by  the  constant  20.  The  result  is  the  square  feet  of 
radiating  surface  per  section.  The  rule  applies  with  least  ac- 
curacy to  the  one-column  radiators. 


108 


HEATING  AND  VENTLATION 


TABLE   X. 


Dimensions  and  Surfaces  of  Radiators,  per  Section. 


Type  of 

jgg 

1  = 

Radiator 

If 

11 
11 

45* 

38" 

32" 

26" 

23" 

221 

20" 

18" 

16" 

141 

lOol.  O.  I  

9  rirkl    fl    T 

5 

8 

3 
3 

5 

3 
4 

2% 

2 

i« 

1% 

9 

o  nnl    fl     T 

9% 

3 

6 

5 

4* 

S3< 

3 

9^ 

4.  rinl    n    T 

11 

10 

8 

6# 

5 

4 

3 

TFlnp  AVIrlP 

3 

6 

4^ 

4 

8 

3 

r 

W 

4W 

1  Ool  Press 

4 

ix 

m 

1 

X 

2  Ool  Press 

9 

4 

8Ji 

2% 

9, 

12% 

R3'! 

4% 

94 

1  Ool.  Wall 

3^ 

riw 

1 

34 

Pressed 

76.  Hot  Water  Heaters: — Heaters  for  supplying  the  hot 
water  to  a  heating  system  may  be  divided  into  three  classes: 
— the  round  vertical,   for  comparatively   small  installations; 
the  sectional,  for  plants  of  medium  size;  and  the  water  tube 
or   fire   tube   heater    with    brick    setting    for    the    larger    in- 
stallations  and   for   central    station    work.      The    round   and 
sectional    types    usually    have    a    ratio    between    grate    and 
heating  surface  of  1  to  20,  while  the  water  tube  or  fire  tube 
heater  will    have,   as  an   average,   1    to    40.      Many   different 
arrangements    of   heating   surface   are    in   use   to-day,   every 
manufacturer  having  a  product  of  particular  merit.     Trade 
catalogs    supply    the    most    up-to-date    literature     on     this 
subject,  but  cuts  of  each  of  the  types  mentioned  above  may 
be  found  in  Fig.  55. 

77.  Steam    Boilers: — The    products    of    many    manufac- 
turers   show    but    little    difference    between    the    hot    water 
heater  and  the  steam  boiler.     The  latter  is  usually  supplied 
with  a  somewhat  larger  dome  to   give   greater  steam   stor- 
age   capacity.      For     heating    purposes,     steam    boilers     fall 
into  the  same  three  classes  as  mentioned  under  water  heat- 


HOT    WATER   AND    STEAM    HEATING 


109 


ers,  having1  about  the  same  ratio  of  heating  surface  to  grate 
surface.  With  the  steam  boiler  generating  steam  at 
5  pounds  gage,  the  temperature  on  one  side  of  the  heating 
surface  is  about  227  degrees,  while  in  a  water  heater  the 
temperature  on  the  same  side  is  about  180  degrees.  Hence, 
with  the  same  temperature  of  the  burning  gases,  the  tem- 
perature difference  is  greater  in  a  water  heater  than  in  a 


Round  Under-Feed 


Sectional  Top  Feed 


Fire  Tube  Type 
Fig.    55. 


110  HEATING  AND  VENTILATION 

boiler,    resulting   in    a   more    rapid   transfer   of    heat,   and   a 
correspondingly  greater  efficiency. 

78.  Combination     Systems: — Combination    systems    are 
frequently   used,  principally  the   one  which   combines  warm 
air  heating   with    either    steam   or   hot  water.      For   such  a 
system  there   is    needed  a  combination   heater,   as   shown  in 
Fig.   20.     It  consists   essentially  of  a  furnace  for  supplying 
warm  air  to  some  rooms,  the  downstairs  of  a  residence  for 
instance,  and  contains  also  a  coil  for  furnishing  hot  water 
to  radiators  located  in  other  rooms,  say,  on  the  upper  floors, 
or  in  places   where   it   would  be   difficult  for  air   to   be   de- 
livered.     Considerable    difficulty    has    been    encountered    in 
properly   proportioning   the    heating   surface  x>f   the   furnace 
to  that  of  the  hot  water  heater,  and  the  systems  have  not 
come  into  general  use. 

79.  Fittings: — Common     and     Special: — Couplings,    elboics 
and  tees,  especially  for  hot  water  work,  should  be  so  formed 
as    to    give   a   free   and    easy   sweep   to    the   contents.      It   is 
highly  desirable  in  hot  water  work  to  use  pipe  bends  of  a 


Fig.  56. 

radius  of  about  five  pipe  diameters,  instead  of  the  common 
elbow.  In  either  case  all  pipe  ends  should  be  carefully 
reamed  of  the  cutting  burr  before  assembling.  This  is 
most  important,  as  the  cutting  burr  is  sometimes  heavy 
enough  to  reduce  the  area  of  the  pipe  by  one-half,  thus 
creating  serious  eddy  currents,  especially  at  the  elbows. 
If  the  single  main  hot  water  system  be  installed,  great 
care  should  be  used  to  plan  the  mains  in  the  shortest  and 
most  direct  routes,  and  the  special  fittings  described  and 
shown  in  Art.  65  should  be  used. 

Eccentric  reducing  fittings  are  often  of  value  In  avoiding 
pockets  in  steam  Lines.  Fig.  56  shows  types  of  these,  which 
should  always  be  used  when,  by  reduction  or  otherwise,  a 


HOT    WATER   AND    STEAM   HEATING 


111 


horizontal  steam  pipe  would  present  a   pocket  for  the   col- 
lection of  condensation  with  its  resultant  water  hammer. 

Valves  for  either  steam  or  hot  water  should  be  of  the 
gate  pattern  rather  than  the  globe  pattern.  The  latter  is 
objectionable  in  hot  water  systems  because  of  the  resistance 
offered  the  stream  of  water,  due  to  the  fact  that  the  axis 
of  the  valve  seat  opening  is  perpendicular  to  the  axis  of 
the  pipe.  The  globe  valve  is  objectionable  in  some 
steam  lines  because  of  the  fact  that  in  a  horizontal  run 
of  pipe  it  forms  very  readily  a  pocket  for  the  collection 
of  condensation,  thus  often  producing  a  source  of  water 
hammer.  In  every  way  gate  valves  are  preferable,  for,  as 
shown  in  Fig.  57,  they  present  a  free  opening  without  turns. 

The  same  caution  applies 
in  the  use  of  check  valves. 
Swing  checks  should  al- 
ways be  specified  rather 
than  lift  checks,  for  the 
former  offer  much  less  re- 
sistance to  the  passage  of 
the  hot  water,  or  the 
steam  and  condensation,  as 
the  case  may  be.  Fig.  58 
shows  a  lift  check  and  a 


Fig.  57. 


swing  check. 


To  avoid  the   annoyance   so  often  experienced  by   leaky 
packing  around  valve  stems,   there  have  been  designed  and 


Fig.   58. 

placed  on  the  market  various  forms  of  packless  valves. 
These  are  to  be  especially  recommended  for  vacuum  work, 
as  the  old  style  valve  with  its  packed  stem  Is,  perhaps,  the 
cause  of  more  failures  of  vacuum  systems  than  any  other 
one  item.  Fig.  59  shows  a  section  of  this  type  of  valve  using 


112 


HEATING  AND  VENTILATION 


the  diaphragm  as  the  flexible  wall.  AU 
packless  valves  will  be  found  to  use  a  dia- 
phragm of  one  form  or  another. 

Quick-opening  Valves,  or  butterfly  valves, 
are  much  used  on  hot  water  radiators;  one- 
quarter  turn  of  the  wheel  or  handle  serves 
to  open  these  full  and,  when  closed,  they 
are  so  arranged  that  a  small  hole  through 
IFlg1.  59.  the  valve  permits  just  enough  leakage  to 

keep  the  radiator  from  freezing.     Special  radiator  valves  for 
steam  may  also  be  obtained. 

Air  valves  have  a  most  important  function  to  discharge. 
As    the   air   accumulates   above    the   water   or    steam   in   the 


radiators,  its  removal  becomes  absolutely  necessary,  if  all 
of  the  radiating  surface  is  to  remain-  effectual.  For  this 
purpose  small  hand  valves  or  pet  cocks,  Fig.  60,  are  in- 
serted near  the  top  of  the  end  section  in  all  hot  water 
work;  and  either  these  same  valves  or  automatic  ones  are 
inserted  for  steam  work.  Valves  are  not  as  essential  on 
two-pipe  steam  systems  as  on  water  or  single-pipe  steam 
systems,  yet  are  generally  used.  For  steam  the  air  valve 
should  be  about  one-third  the  radiator  height  from  the  top. 

Fig.  61  shows  a  common  type 
of  automatic  air  valve  using  the 
principle  of  the  expansion  stem.  As 
long  as  the  air  flows  around  the 
stem  and  exhausts,  the  stem  re- 
mains contracted,  and  the  needle 
valve  open;  but  when  the  hot  steam 
enters  and  flows  past  the  expansion 
stem,  it  lengthens  sufficiently  to  close  the  needle  valve.  In 
other  forms  of  air  valves  the  heat  of  the  steam  closes  the 
needle  valve  by  the  expansion  of  a  volatile  liquid  in  a  small 
closed  retainer.  In  still  other  forms  the  lower  part  of  the 
valve  casing  is  filled  with  water  of  condensation  upon 
which  floats  an  inverted  cup,  having  air  entrapped  within. 


Fig.   61. 


HOT    WATER   AND    STEAM   HEATING 


113 


This   cup   carries   the   needle   of  the  valve   at  its   upper   ex- 
tremity, the  heat  of  the  steam  expanding  the  air  sufficiently 
to  raise  the  cup  and  close  the  valve.    Where  the  system  is  de- 
signed to  act  as  a  gravity  installation,  special  air  valves  must 
be  used  which  will  not  allow  air  to  enter  at  any  time.     Fig. 
62  shows  a  type   of  automatic  valve   designed  to  accommo- 
date larger  volumes  of  air  with  promptness, 
as  when  a  long  steam  main  or  large  trap  is 
to  be  vented.     This  type  employs  a  long  cen- 
tral tube,  as  shown,  which  carries  at  the  top 
the    valve    seat    of    the    needle    valve.      The 
needle  itself  is  carried  by  the  two  side  rods. 
As    long    as    the    air    flows    up    through    the 
central    pipe,    the    needle    valve    will    remain 
open;    but   when   hot   steam   enters   the   tube, 
it    expands,    and    carries    the    valve    seat    up- 
ward   against    the    needle,    thus    closing    the 
valve.     The  size  and  strength  of  parts  makes 
this  form  a  very  reliable  one. 
The  expansion  tank,   Fig.    63,    for  a   hot   wat- 
er system  is  often  located  in  the  bath  room  or 
closet   near  the   bath   room   and   its   overflow 
connected  to  proper  drainage.      It   should  be 
at    least    2    feet    above    the    highest    radiator. 
The  connection  to  the  heating  system  mains 
Is  most  often  by  a  branch  from  the  nearest 
radiator  riser,   or   it  may  have   an   independ- 
ent riser  from  the   basement  flow  main.  The 
capacity    of    the    tank    is    usually    taken    at 
about    one-twentieth    of    the    volume    of    the 
entire  system,   or  a  more  easily  applied  rule 
is  to  divide  the  total  radiation  by  40  to  obtain  the 
capacity  of  the   tank   in  gallons.      See    Table    39,  Appendix. 


Fig.   62. 


Fig.   63. 


CHAPTER  VIII. 


HOT  \VATER  AND  STEAM  HEATING. 


PRINCIPLES    OF   THE   DESIGN,    WITH    APPLICATION. 

In  a  hot  water  or  steam  system,  the  first  important 
item  to  be  determined  by  calculation  is  the  amount  of 
radiation,  in  square  feet,  to  be  installed  in  each  room. 
Nearly  all  other  items,  such  as  pipe  sizes,  boiler  size,  grate 
area,  etc.,  are  estimated  with  relation  to  this  total  radia- 
tion to  be  supplied.  The  correct  determination,  then,  of 
the  square  feet  of  radiation  in  these  systems  is  all-im- 
portant. 

80.  Calculation  of  Radiator  Surface: — Considering  the 
standard  room  of  Chapter  III,  where  the  heat  loss  was  de- 
termined to  be  14000  B.  t.  u.  per  hour  on  a  zero  day,  the 
problem  is  to  find  what  amount  of  surface  and  what  size  of 
radiator  will  deliver  14000  B.  t.  u.  per  hour  to  the  room, 
under  the  conditions  as  given.  Experiments  by  numerous 
careful  investigators  have  shown  that  the  ordinary  cast  iron 
radiator,  located  within  the  room  and  surrounded  with  com- 
paratively still  air,  gives  off  heat  at  the  rate  of  1.7  B.  t.  u. 
(1.6  to  1.8,  or  1.7  average)  per  square  foot  per  degree 
difference  between  the  temperature  of  the  surrounding  air 
and  the  average  temperature  of  the  heating  medium,  per 
hour.  This  is  called  the  rate  of  transmission.  With  hot 
water  the  average  conditions  within  the  radiator  have 
been  found  to  be  as  follows:  temperature  of  the  water  en- 
tering the  radiator  180  degrees;  leaving  the  radiator  160 
degrees;  hence,  the  average  temperature  at  which  the  in- 
terior of  the  radiator  is  maintained  is  170  degrees.  Since, 
in  this  country,  the  standard  room  temperature  is  70  de- 
grees, and,  for  hot  water,  the  "degree  difference"  is  170  — 
70  =  100,  then  a  hot  water  radiator  will  give  off  under 
standard  conditions  1.7  X  100  =  170  B.  t.  u.  per  sq.  ft.  per  hour. 
The  temperature  within  a  steam  radiator  carrying  steam  at 
pressures  varying  between  2  and  5  pounds  gage  is  usually 
taken  at  220  degrees,  and  the  total  transmission  is  approx- 
imately 1.7  X  (220  —  70)  =  255  B.  t.  u.  per  square  foot  per 


HOT  WATER  AND  STEAM  HEATING  115 

hour.  The  general  formula  for  the  square  feet  of  radiation, 
then,  is 

R  —         Total   B.  t.    u.   lost  from  the  room   per  hour 

1.7  (Temp.  diff.  between  inside  and  outside  of  rad.) 

For  hot  water,  direct  radiation  heating,  this  becomes,  to  the 
nearest  thousandth 

R»  = =   .006  H  (30) 

1.7   (170  —  70) 

For  steam,  direct  radiation 

n 

Rs  = =    .004  H  (31) 

1.7   (220  —  70) 

Rule. — To  find  the  square  feet  of  radiation  for  any  room  divide 
the  calculated  heat  loss  in  B.  t  u.  per  hour  by  the  quantity  1.7 
times  the  difference  in  temperature  between  the  inside  and  the  out- 
side of  the  radiator. 

It  will  be  noticed  from  (30)  and  (31)  that  Rw  —  1.5.  R*  which 
accounts  for  the  practice  that  some  people  have  of  finding 
all  radiation  as  though  it  were  steam,  and  then,  when  hot 
water  radiation  is  desired,  adding  50  per  cent,  to  this 
amount. 

APPLICATION. — From  the  standard  room  under  considera- 
tion, formula  30  gives  Rw  =  .OC6  X  14000  =  84  square  feet 
of  radiator  surface  for  hot  water;  and  formula  31  gives  R> 
=.  .004  X  14000  =  56  square  feet  of  radiator  surface  for 
steam.  From  these  values  the  number  of  sections  of  a  giv- 
en type  of  radiator  can  be  determined  by  dividing  by  the 
area  of  one  section,  as  explained  in  the  preceding  chapter. 
The  length  of  the  radiator  may  also  be  found  from  this 
same  table,  by  noting  the  thickness  of  the  section*,  and 
multiplying  by  their  number. 

Formulas  30  and  31  give  the  standard  ratios  be- 
tween the  heat  loss  and  direct  radiation.  If,  however,  the 
radiation  is  installed  as  direct -indirect,  it  is  quite  common 
practice  to  increase  the  amount  of  direct  radiation  by  25 
per  cent,  to  allow  for  the  ventilation  losses.  On  this  basis 
formulas  30  and  31  become,  respectively, 

Rw  =  .0075  H  (32) 

R»  =   .005     H  (33) 

Duct  sizes  for  properly  accommodating  the  air  In 
direct-indirect  heating  may  be  taken  from  the  following: 


116  HEATING  AND  VENTILATION 

To  obtain  the  duct  area,  in  square  inches,  multiply  the  square  feet 
of  radiation  by  .75  to  1  for  steam,  and  by  .5  to  .75  for  hot  water. 
{To  obtain  the  amount"  of  air  which  may  be  expected  to  enter  and 
pass  through  the  radiator  into  the  room,  multiply  the  square  feet 
of  radiation  by  100  for  steam,  or  by  75  for  hot  water.  This  gives 
the  cubic  feet  of  air  entering-  per  hour. 

Again,  if  the  radiation  is  installed  as  purely  indirect, 
yet  not  as  a  plenum  system,  it  is  common  to  increase  the 
amount  of  direct  radiation  by  50  per  cent.  Now  formulas  30  and 
31  become,  respectively, 

Rw  —  .009  H  (34)-a 

Rs  =  .006  H  (34)-b 

For  proportioning  the  duct  sizes  in  indirect  heating 
use  the  following  table.  To  obtain  the  duct  area  in  square 
inches,  multiply  the  square  feet  of  radiation  installed  by 

Steam  Hot  Water 

First  Floor  1.5  to  2.0  1.0     to  1.33 

Second   Floor  1.0  to  1.25  .66  to      .83 

Other  Floors  .9  to  1.0  .6     to      .66 

Vent  ducts,  where  provided,  are  usually  taken  .8  of  the 
area  of  supply  ducts.  Also,  for  finding  the  amount  of  air  in 
cubic  feet,  which  may  be  reasonably  expected  to  enter 
under  these  conditions,  Carpenter  gives  the  following: 
Multiply  the  square  feet  of  indirect  radiation  by 

Steam  Hot  Water 
First    Foor                        200  150 

Second   Ploor  170  130 

Other  Floors  150  115 

If  this  amount  of  air  is  insufficient  for  the  desired  degree 
of  ventilation,  more  air  must  be  brought  in  by  correspond- 
ingly larger  ducts,  and  for  each  300  cubic  feet  additional 
with  steam,  or  each  200  cubic  feet,  additional  with  hot 
water,  add  one  square  foot  to  the  radiation  surface. 

A  steam  system  may  be  installed  to  work  at  any  pres- 
sure, from  a  vacuum  of,  say,  10  pounds  absolute,  to  as  high 
a  pressure  as  75  pounds  absolute.  To  calculate  the  prop- 
er radiation  for  any  of  these  conditions  use  formula  31  or 
its  derivatives,  and  substitute  the  proper  steam  tempera- 
ture in  place  of  220  degrees. 

In  like  manner,  to  find  the  amount  of  hot  water  radi- 
ation for  any  other  average  temperatures  of  the  water 


HOT    WATER   AND   STEAM   HEATING  117 

than  the  one  given,  merely  substitute  the  desired  average 
temperature  in  the  place  of  170.  One  point  should  be  re- 
membered, the  maximum  drop  in  temperature  as  the  water 
passes  through  the  heater  will  seldom  be  more  than  20 
degrees,  even  under  severe  conditions.  More  often  it  will 
be  less,  but  this  value  is  used  in  calculations.  Again,  the 
temperature  of  the  entering  water  may  be  at  the  boiling 
point,  if  necessary,  thus  causing  each  square  foot  of  sur- 
face to  be  more  efficient  and  consequently  reducing  the  to- 
tal radiation  in  the  room.  To  illustrate,  try  formula  30 
with  a  drop  in  temperature  from  210  to  190  degrees  and  find 
64  square  feet  of  radiator  surface  for  this  room.  Since  a 
radiator  always  becomes  less  efficient  from  continued  use,  it 
is  best  to  design  a  system  with  a  lower  temperature  as 
given  in  the  formula,  and  then,  if  necessary  under  stress 
of  conditions,  this  system  may  be  increased  in  capacity  by 
increasing  the  water  temperature  up  to  the  boiling  point. 
81.  Empirical  Formulas: — All  of  the  above  formulas  may 
be  considered  as  rational  and  checked  by  years  of  experience 
and  application.  Many  empirical  formulas  have  been  de- 
vised in  an  attempt  to  simplify,  but  the  results  are  always 
so  untrustworthy  that  the  rules  are  w.orthless  unless  used 
with  that  discretion  which  comes  only  after  years  of  prac- 
tical experience.  Many  of  these  rules  are  based  on  the 
cubic  feet  of  volume  heated,  without  any  other  allowance, 
these  being  given  anywhere  from  one  square  foot  of  steam 
surface  per  30  cubic  feet  of  space,  to  one  square  foot  to 
100  cubic' feet.  The  extreme  variation  itself  shows  the  un- 
reliableness  of  this  method,  and  under  no  conditions  should 
it  be  used  for  proportioning  radiating  surface.  Various 
central  heating  companies,  and  others,  proportion  radia- 
tors for  their  plants  according  to  their  own  formulas, 
among  which  the  following  may  be  noted. 

a     w      G  G     w        c 

(a)  Rw  = 1 1 Rs  = h H 

2         10         60  2         10          200 

2 

(b)  Rw  -  G  +  .05  W+  .01  C      R»  =  —  «?  +  .05  W  +  .01  C) 

(c)  Rw  =  .75  G  +  .10  W  +  .01  C      Rs  —  .5  G  +  -05  W  +  .005  G 
It  is  evident  that  these  are  really  simplified  forms  of  Car- 
penter's   original    formula.      When    applied    to    the    sitting 
room,   where   Carpenter's   formula   gave,    for  hot   water   and 
steam,   84   square   feet  and   56   square   feet,    respectively,    (a) 


118  HEATING  AND  VENTILATION 

gives    85.5   and    63,    (b)    gives    75   and    50,   and   (c)    gives   82.5 
and  46  respectively. 

Another  approximate  rule  devised  by  John  H.  Mills 
anJ  still  used  to  some  extent  is  "Allow  1  square  foot  of 
steam  radiation  for  every  200  cubic  feet  of  volume,  1  square 
foot  for  every  20  square  feet  of  exposed  wall  and  1  square 
foot  for  every  2  square  feet  of  exposed  glass."  Applying 
this  to  the  standard  room,  it  gives  9.75  +  13.25  +  18  =  41 
square  feet  of  steam  radiation  as  against  56  square  feet 
by  rational  formula.  This  shows  a  considerable  difference 
from  the  rules  preceding. 

82.  Greenhouse  Radiation: — The  problem  of  properly 
proportioning  greenhouse  radiation  is  considered,  by  some, 
of  such  special  nature  as  to  justify  the  use  of  empirical 
formulas.  The  fact  that  the  glass  area  is  so  large  compared 
to  the  wall  area  and  the  volume,  combined  with  the  fact 
that  the  head  of  water  in  the  system  is  small  and  that  the 
radiation  surface  is  usually  built  up  as  coils  from  1%,  1%  or 
2  inch  wrought  iron  pipe,  gives  rise  to  a  problem  that  differs 
essentially  from  that  of  a  room  of  ordinary  construction.  It 
is  not  surprising,  therefore,  to  find  a  great  variety  of  empir- 
ical formulas  desigrted  exclusively  for  this  work.  Whatever 
merit  these  may  1  ave,  they  do  not  give  the  assurance  that 
comes  from  the  application  of  rational  formulas.  It  is  always 
best  to  use  rational  formulas  first  and  then  check  by  the 
various  empirical  methods. 

Formulas  30  and  31,  stated  in  Art.  80,  when  properiy 
modified,  are  applicable  to  greenhouses  and  give  very  re- 
liable results.  As  stated  above,  the  radiating  surface  is 
usually  that  of  wrought  iron  pipes  hung  below  the  flower 
benches  or  along  the  side  walls  below  the  glass.  The  trans- 
mission constant,  K,  for  wrought  iron  or  mild  steel  is  2.0  to 
2.2  B.  t.  u.  per  square  foot  per  degree  difference  per  hour, 
making  the  total  transmission  per  square  foot  of  coil  surface 
per  hour  about  2(170  —  70)  =  200  for  hot  water,  and  2(220 
—  70)  =  300  for  steam.  These  values  may  be  safely  used. 
The  only  necessary  modification  of  the  two  formulas  men- 
tioned, consists  in  replacing  the  constant  1.7  by  2,  giving 
for  hot  water  g 

Rw  =  =    .005  H  (35)-a 

2(170  —  70) 
And  for  steam 

R-  =    2(220-70)       =   -0033  " 


HOT    WATER   AND    STEAM    HEATING  119 

If,  however,  the  highest  temperature  at  which  it  is  desirable 
to  maintain  the  house  in  zero  weather  is  other  than  70  de- 
grees, this  temperature  should  be  used  instead  of  70. 

In  a  greenhouse  there  is  very  little  circulation  of  air, 
hence  the  heat  loss,  H,  would  be  found  from  the  equivalent 
glass  area  i.  e.,  ((?  +  .25  TF).  Formulas  35-a  and  &  would 
then  reduce  to  Rw  =  .35  (O  +  .25  W)  and  R*  =  .23  (G  +  .25  W). 
It  is  noticed  that  these  values  give  about  one  square  foot  of 
H.  W.  radiation  to  2.8  square  feet  of  equivalent  glass  area,  and 
one  square  foot  of  steam  radiation  to  4.4  square  feet  of  equivalent 
glass  area  as  approximate  rules.  These  figures  should  "be  considered 
a  minimum. 

Empirical  rules  for  greenhouse  radiation,  quoted  by 
many  firms  dealing  in  the  apparatus,  are  usually  given  in 
the  terms  of  the  number  of  square  feet  of  glass  surface 
heated  by  one  lineal  foot  of  1%  inch  pipe.  A  very  commonly 
quoted  and  accepted  rule  is,  one  foot  of  1^4  inch  pipe  to 
every  2*4  square  feet  of  glass,  for  steam;  or,  one  foot  of 
iy±  inch  pipe  to  every  1%  square  feet  of  glass,  for  hot  water, 
when  the  interior  of  the  house  is  70  degrees  in  zero  weather. 
Table  XI,  taken  from  the  Model  Boiler  Manual,  shows 
the  amount  of  surface  for  different  interior  temperatures 
and  different  temperatures  of  the  heating  medium. 

In  general,  it  may  be  said  that  in  greenhouse  heating, 
great  care  should  be  used  in  the  rating  and  the  selection 


STEAM 

Fig.   64. 

of  the  boilers  or  heaters.  It  is  well  to  remember  that  the 
severe  service  demanded  by  a  sudden  change  in  the  weather 
is  much  more  difficult  to  meet  in  greenhouses  than  in  ordin- 
ary structures,  and  that  a  liberal  reserve  in  boiler  capacity 
is  highly  desirable. 

If  any  greenhouse  under  consideration  can  be  heated 
from  some  central  plant  where  the  heat  will  be  continuous 
throughout  the  night  with  a  man  in  charge  at  all  times, 


120 


HEATING  AND  VENTILATION 


then  steam  is  very  desirable  because  of  the  reduced  amount 
of  heating  surface  necessary.  If,  however,  in  cold  weather 
the  steam  pressure  to  be  allowed  to  drop  during  the  night- 
time, then  hot  water  should  be  used.  This  permits  a  better 
circulation  of  heat  throughout  the  greenhouse  during  the 
night.  The  same  rules  apply  in  running  the  mains  and 
risers  as  would  apply  in  the  ordinary  hot  water  and  steam 
systems.  In  greenhouse  work  the  head  of  water  is  very 
low  and  this  makes  the  circulation  rather  sluggish  but  with 
sufficient  pipe  area  and  a  minimum  friction  a  hot  water 
system  may  be  used  with  satisfaction.  In  some  houses  the 
coils  are  run  along  the  wall  below  the  glass  and  supported 
on  wall  brackets,  in  others  they  are  run  underneath  the 
benches  and  supported  from  the  benches  with  hangers, 
while  in  greenhouses  with  very  large  exposure  there  are 
sometimes  required  both  wall  and  bench  coils.  In  all  of 
these  piping  layouts  it  is  necessary  that  a  good  rise  and 
fall  be  given  to  the  pipes.  Fig.  64  shows  two  systems  of 
pipe  connections,  one  where  the  steam  or  flow  enters  the 
coils  from  above  the  benches  and  the  other  where  it  enters 
from  below,  the  return  in  each  case  being  at  the  lowest 
point.  These  bench  coils  could  be  run  along  the  wall  with 
equal  satisfaction. 

TABLE  XL 


Temperature  of 
Air  in  House 

Temperature  of  Water  in  Heating  Pipes 

Steam 

110° 

160° 

180° 

200° 

Three  Ibs. 
Pressure 

Square  fee*t  of  glass  and  its  equivalent  proportioned  to 
one  square  foot  of  surface  in  heating  pipes  or  radiator 

40° 
45° 
50° 
55° 
60° 
65° 
700 
75° 
800 
85° 

4.33 
3.63 
8  07 
2  63 
2.19 
1.86 
1-58 
1.37 
1.16 
.99 

5.25 
4-65 
8-92 
8.89 
2-89 
2  53 
2.19 
1.92 
1.63 
1.42 

6  66 
5  55 
4  76 
4.16 
8-63 
8  22 
2.81 
2  5 
2.17 
1.92 

7-69 
6.66 
5.71 
5. 
4.83 
3-84 
8  44 
8.07 
2  78 
2.46 

8. 
7-6 
7. 
6.5 
6. 
5.5 
5. 
4-5 
4. 
8.5 

7.5 
6.75 
6.0 
5.5 
5.0 
4.5 
4.25 
4.0 
3.75 
3.5 

This    table    is    computed    for    zero    weather;    for    lower 
temperatures  add  1%  per  cent,  for  each  degree  below  zero. 


HOT    WATER   AND    STEAM   HEATING  121 

The  last  column  in  Table  XI  has  been  calculated  from 
formula  35-b  and  added  for  purpose  of  comparison. 

APPLICATION. — Given  an  even  span  greenhouse  25  ft.  wide, 
100  ft.  long  and  5  ft.  from  ground  to  eaves  of  roof,  having 
slope  of  roof  with  horizontal  35°.  Ends  to  be  glass  above 
the  eaves  line.  What  amount  of  hot  water  radiation  with 
water  at  170°  and  what  amount  of  low  pressure  steam  radia- 
tion would  be  installed? 

Length  of  slope  of  roof  =  12.5  ^  cos.  35°  =  15.25. 

Area  of  glass  =  15.25  X  100  X  2  +  2  X  12.5  X  8.8  =  3270 
sq.  ft. 

Area  of  wall  =  5X100X2  +  5X25X2  =  1250  sq.  ft. 

Glass  equivalent  =  3270  +  .25  X  1250  =  3582.5  sq.  ft. 

Rw=  .35  X  3582.5  =  1253.8  sq.  ft. 

J{a  =  .23  X  3582.5  =    824.  *  sq.  ft. 

From  Table  XL 

R»=  3582.5  -T-  2.5  =  1433  sq.  ft. 

Rs  =  3582.5  ^5      =     716.  .sq.   ft. 

*Check  with  last  column  of  Table  XI. 

83.  The  Determination  of  Pipe  Sizes: — The  theoretical 
determination  of  pipe  sizes  in  hot  water  and  steam  systems 
has  always  been  more  or  less  unsatisfactory,  first,  because 
of  the  complicated  nature  of  the  problem  when  all  points 
having  a  bearing  upon  the  subject  are  considered,  and 
second,  because  it  is  almost  an  impossibility  to  even  ap- 
proximate the  friction  offered  by  different  combinations  and 
conditions  of  piping.  The  following  rather  brief  analysis 
gives  a  theoretical  method  for  determining  pipe  sizes  where 
friction  is  not  considered. 

In  a  hot  water  system  let  the  temperatures  of  the  water 
entering  and  leaving  the  radiator  be,  respectively,  180 
and  160  degrees;  then  it  is  evident  that  one  pound  of  the 
water  in  passing  through  the  radiator,  gives  off  20  B.  t.  u. 
Under  these  conditions  the  standard  room  would  have  14000  -f- 
20  =  700  pounds  of  water  passing  through  the  radiator  per 
hour.  Converting  this  to  gallons,  it  is  found  to  be  84.03. 
But  the  radiation  for  this  room  was  found  to  be  84  square 
feet.  Therefore,  it  may  be  said  that  a  hot  water  radiator 
unde~  normal  conditions  of  installation  and  under  heavy 
service  requires  one  gallon  of  water  per  square  foot  of  sur- 
face per  hour.  Knowing  the  theoretical  amount  of  water 
per  hour,  it  remains  only  to  obtain  the  theoretical  speed 


122  HEATING   AND    VENTILATION 

at  which  it  travels,  due  to  unbalanced  columns,  to  obtain 
finally,  by  division,  the  theoretical  area  of  the  pipe. 

Consider  a  radiator  to  be  about  10  feet  above  the 
source  of  heat,  and  the  temperature  in  the  flow  riser  to  be 
180  degrees  and  in  the  return  riser  160  degrees,  good  values 
in  practice.  Now  the  heated  water  in  the  flow  riser 
weighs  60.5567  pounds  per  cubic  foot,  while  that  in  the 
return  riser  weighs  60.9697  pounds  per  cubic  foot.  The  mo- 

,  TF  —  W    \ 

tive  force  is  f  =•  g   {    I  where  g  is  the  acceleration 

V  w   +   W  / 

due  to  gravity,  W  is  the  specific  gravity  (weight)  of  the 
cooler  column  and  W  is  the  specific  gravity  (weight)  of  the 
warmer  column.  Substitute  /  for  g  in  the  velocity  formula 
and  obtain  v  =  \/2fh  and 


/  W  —  W   \ 
i  (   -  ) 

V  w  +  w    i 


(36) 
Inserting  values  W,  W  and  assuming  Ji  =  10  feet,   we  have 


v  =  V2  X  32.2  X  10  X  .0034  =  V2.1896  —  1.47  feet  per  second. 
From  this  it  has  become  a  custom  to  speak  of  1.5  feet  per 
second  or  5400  feet  per  hour,  as  the  theoretical  velocity  of 
water  in,  say,  a  first  floor  riser,  disregarding  the  effect  of 
all  friction  and  horizontal  connections.  Theoretical  veloci- 
ties for  any  other  height  of  column  and  for  other  temper- 
atures may  be  obtained  in  like  manner.  Continuing  this 
special  investigation  and  changing  the  84  gallons  per  hour 
to  cubic  inches  per  hour  by  multiplying  by  231,  the  internal 
pipe  area  may  be  obtained  by  dividing  by  the  unit  speed 
per  hour  which  gives  (84  X  231)  ~-  (5400  X  12)  =  .3  square 
inch.  This  corresponds  to  approximately  a  %  inch  pipe 
and  without  doubt,  would  supply  the  radiator  if  the  sup- 
position of  no  frictional  resistances  could  be  realized.  This 
ideal  condition,  of  course,  cannot  be  had,  nor  can  the  fric- 
tion in  the  average  house  heating  plant  be  theoretically 
treated  with  any  degree  of  satisfaction.  Hence  it  is  still 
the  custom  to  use  tables  for  the  selection  of  pipe  sizes, 
based  upon  what  experience  has  shown  to  be  good  practice. 
Such  tables,  from  various  authorities,  may  be  found  in  the 
Appendix.  It  is  safe  to  say  that  one  should  never  use  any- 
thing smaller  than  a  1  inch  pipe  in  low  pressure  hot  water 
work. 

With  steam  systems,  where  the  heating  medium  is  a  vapor, 


HOT   WATER   AND    STEAM   HEATING  123 

and  subject  in  a  lesser  degree  to  friction,  the  discrepancy 
between  the  theoretical  and  the  practical  sizes  of  a  pipe 
is  not  so  great  as  in  hot  water.  Each  pound  of  steam,  in 
condensing,  gives  off  approximately  1154  —  181  =  973  B.  t.  u. 
To  supply  the  heat  loss  of  the  standard  room,  14000  B.  t.  a. 
per  hour,  it  would  require  14.5  pounds  of  steam  per  hour. 
When  it  is  remembered  that  the  calculated  surface  of  the 
direct  steam  radiator  for  this  room  was  56  square  feet,  it 
appears  that  a  radiator,  under  stated  conditions  and  under  a 
heavy  service,  requires  one-fourth  of  a  pound  of  steam  per  square 
foot  of  surface  per  hour.  This  may  be  shown  in  another  way: 
each  square  foot  of  steam  radiation  gives  off  255  B.  t.  u. 
per  hour;  then,  each  square  foot  will  condense  255  -5-  973  = 
.26  +  pounds  of  steam  per  hour. 

Now  the  volume  of  the  steam  per  pound  at  the  usual 
steam  heating  pressure,  18  pounds  absolute,  is  21.17  cubic 
feet.  Since  the  standard  room  radiator  required  14.5  pounds 
per  hour,  it  would,  in  that  time,  condense  steam  corres- 
ponding to  a  void  of  21.17  X  14.5  =  307  cubic  feet  per  hour. 
This  is  the  volume  of  the  steam  required  by  the  radiator, 
and,  if  the  speed  of  the  steam  in  the  pipe  lines  be  taken 
at  15  feet  per  second,  or  54000  feet  p,er  hour,  the  area  of 
the  pipe  would  be  307  X  144  -r-  54000,  or  .82  square  inch, 
corresponding  very  closely  to  a  1  inch  pipe.  For  a  two- 
pipe  system  this  would  be  considered  good  practice  under 
average  conditions;  but  in  a  one-p*ipe  system,  where  the 
condensation  is  returne.d  against  the  steam  in  the  same 
pipe  that  feeds,  a  pipe  one  size  larger  would  be  taken. 

Table  35,  Appendix,  calculated  from  Unwin's  formula, 
may  be  used  in  finding  sizes  and  capacities  of  pipes  carrying 
steam.  In  addition  to  this,  Tables  31,  32,  33  and  34  give  sizes 
that  are  recommended  by  experienced  users. 

For  a  theoretical  discussion  of  loss  of  head  by  friction 
in  hot  water  and  steam  pipes,  .see  Arts.  147  and  175. 

84.  Grate  Area: — To  obtain  the  grate  area  for  a  direct 
radiation  hot  water  or  steam  system  by  the  B.  t.  u.  method, 
the  same  analysis  as  found  in  Chapter  IV  may  be  applied. 
The  total  B.  t.  u.  heat  loss,  H,  is  that  calculated  by  the 
formula  and  does  not  include  Hv,  the  heat  loss  due  to  ven- 
tilation, since  with  the  direct  hot  water  or  steam  system  as 
usually  installed  no  ventilation  is  provided.  In  any  special 
case  where  ventilation  is  provided  in  excess,  use  H'  instead 
of  H.  The  commercial  rating  of  heaters  and  boilers  is  a 


124  HEATING  AND  VENTILATION 

subject  each  day  receiving  greater  attention  at  the  hands 
of  manufacturers;  yet  it  is  a  subject  where  much  uncer- 
tainty is  felt  to  exist.  Hence  the  recommendation,  "Always 
check  grate  area  by  an  actual  calculation,"  rather  than  rely 
entirely  upon  the  catalog  ratings. 

85.  Pitch  of  Mains: — The  pitch  of  the  mains  is  quite  as 
important  in  hot  water  as   in  steam  work.     This  should  be 
not  less  than  1  inch  in  10  feet  for  hot  water  systems,  and  not 
less    than    1    inch    in    30    feet    for    steam    systems.      Greater 
pitches   than    these   are    desirable,    but   not   always    practic- 
able.    In  hot  water  plants  the  pitch  of  the  basement  mains, 
whether  flow   or  return,    is  upward   as   these   mains   extend 
from  the   source   of   heat,   that   is,   the   highest   point   is   the 
farthest  from  the  heater.     In  steam  plants  the  mains,  under 
any    condition     of    arrangement,    always     pitch     downward 
in  the  direction  of  the  flow  of  the  condensation. 

86.  Location    and    Connection    of   Radiators: — In    locat- 
ing radiators,  it  is  best  to  place  them  along  the  outside  or 
the    exposed    walls.      When    allowable,    under    the    windows 
seems   to    be    a    favorite    position.      Especially    in    buildings 
of  several  stories,  the   radiators  should  be  arranged,  where 
possible,    in   tiers,    one   vertically    above    another,    thus    re- 
ducing the  number  of  and  avoiding  the  offsets  in  the  risers. 
In  the  one-pipe  system  any  number  of  radiators  may  be  con- 
nected to  the   same   riser.     In  the  two-pipe   system   several 
radiators  may  have  either  a  common  flow  riser,  or  a  common 
return  riser,   but   should  never  have   both,   either   with   hot 
water  or  with  steam. 

The  connections  from  the  risers  to  the  radiators  should 
be  slightly  pitched  for  drainage  and  are  usually  run  along 
the  ceiling  below  the  radiator  connected.  These  connections 
should  be  at  least  two  feet  long  to  give  that  flexibility  of 
connection  to  the  radiator  made  necessary  by  the  expan- 
sion and  contraction  of  the  long  riser.  Similarly,  all  risers 
should  be  connected  to  the  mains  in  the  basement  by  hori- 
zontals of  about  two  feet  to  allow  for  the  expansion  and 
contraction  of  the  mains.  A  system  thus  flexibly  connected 
stands  in  much  less  danger  of  developing  leaky  joints  than 
does  one  not  so  connected.  For  sizes  of  radiator  connections 
see  Table  29,  Appendix. 


HOT   WiATER   AND   STEAM   HEATING  125 

87.  General  Application: — Figs.  65,  66  and  67  show  the 
typical  layout  of  a  hot  water  plant.  Due  to  the  similarity  be- 
tween hot  water  and  steam  installations,  the  former  only  will 
be  designed  complete.  In  attempting  the  layout  of  such  a 
system,  the  very  first  thing  to  be  done  is  to  decide  at  what 
points  in  the  rooms  the  radiators  should  be  placed.  This 
should  be  done  in  conjunction  with  the  owner  as  he  may 
have  particular  uses  for  certain  spaces  from  which  radia- 
tors are  hence  excluded.  The  first  actual  calculation  should 
be  the  heat  loss  from  each  room,  with  the  proper  exposure 
losses,  and  the  results  should  be  tabulated  as  the  first 
column  of  a  table  similar  to  Table  XII.  In  the 
example  here  given,  this  loss  is  the  same  as,  and  taken 
from,  the  table  of  computations  for  the  furnace  work,  Art. 
48,  the  house  plans  being  identical.  The  second  column 
of  Table  XII,  as  indicated,  is  the  square  feet  of  radiation; 
and  since  this  is  a  hot  water,  direct  radiation  system,  it 
is  obtained  by  taking  .006  of  the  items  in  the  first  column 
according  to  formula  30.  Knowing  this,  a  type  and 
height  of  radiator  can  be  selected,  and  the  number  of 
sections  determined  by  Table  X.  Next  obtain  the  lengths 
of  radiators  by  multiplying  the  number  of  sections  by  the 
total  thickness  of  the  sections,  as  given  in  Table  X,  and 
determine  whether  or  not  the  radiator  of  such  a  length 
will  fit  into  the  chosen  space.  If  not,  then  a  radiator  of 
greater  height  and  larger  surface  per  section  must  be 
selected.  Riser  sizes  and  connections  may  be  taken  ac- 
cording to  Tables  31  and  29  respectively.  The  column  of 
Table  XII  headed  "Radiators  Installed"  gives  first  the  num- 
ber of  sections;  second,  the  height  in  inches;  and  third,  the 
number  of  columns  or  type-  of  the  section. 

Locate  radiators  on  the  second  floor  and  transfer  the 
location  of  their  riser  positions  to  first  floor  plan,  then  to 
the  basement  plan.  Locate  radiators  on  the  first  floor  and 
transfer  their  riser  locations  to  the  basement  plan,  which 
will  then  show,  by  small  circles,  the  points  at  which  all 
risers  start  upward.  This  arrangement  will  aid  greatly  in 
the  planning  of  the  basement  mains. 

The  keynotes  in  the  layout  of  the  basement  mains 
should  be  simplicity  and  directness.  If  the  riser  positions 
show  approximately  an  even  distribution  all  around  the 
basement,  it  may  be  advisable  to  run  the  mains  in 


126  HEATING  AND  VENTILATION 

complete  circuits  around  the  basement.  If,  again,  the 
riser  positions  show  aggregation  at  two  or  three  localities, 
then  two  or  three  mains  running  directly  to  these  localities 
would  be  most  desirable.  As  an  example,  take  the  applica- 
tion shown  here.  The  basement  plan  shows  three  clusters 
of  riser  ends,  one  under  the  kitchen,  another  under  the 
study,  and  a  third  on  the  west  side  of  the  house.  This 
condition  immediately  suggests  three  principal  mains,  as 
shown.  The  main  toward  the  kitchen  supplies  the  bath, 
chamber  4  and  the  kitchen,  making  a  total  of  131  square 
feet.  Being  only  about  13  feet  long,  it  would  readily  carry 
this  radiation  if  of  2  inch  diameter.  See  Table  34,  Appendix. 
The  main  to  the  study  and  the  hall  supplies  chamber  1,  the 
hall  and  the  study,  making  a  total  of  221  square  feet,  which 
can  be  carried  by  a  2l/2  inch  pipe.  The  main  to  the  west  side 
of  the  house  supplies  chamber  2,  chamber  3,  the  sitting  room 
and  the  dining  room,  a  total  of  249  square  feet,  which  would 
almost  require  a  3  inch  main,  according  to  the  table,  were 
it  not  for  its  comparatively  short  length.  A  2y2  inch  pipe 
would  amply  supply  this  condition. 

In  hot  water  work,  as  well  as  in  steam,  it  is  customary 
to  take  the  connections  to  flow  risers  from  the  top  of  the 
mains,  thus  aiding  the  natural  circulation,  Fig.  35.  If  not 
taken  directly  from  the  top  of  the  main,  it  is  often  taken  at 
about  45  degrees  from  the  top.  This  arrangement,  with  a 
short  nipple,  a  45  degree  elbow,  and  the  horizontal  connec- 
tion about  iy2  to  2  feet  long,  makes  a  joint  of  sufficient 
flexibility  between  the  main  and  riser  to  avoid  expansion 
troubles. 

In  the  selection  of  a  heater  or  boiler  much  that  has 
been  said  concerning  furnaces  applies.  The  heater  or  boiler 
should,  above  all,  have  ample  grate  area,  checked  on  a  B. 
t.  u.  basis,  and  should  have  a  sufficient  heating  surface  so 
designed  that  the  heated  gases  from  the  fire  impinge  per- 
pendicularly upon  it  as  often  as  may  be  without  seriously 
reducing  the  draft.  As  shown  by  the  total  of  the  radiation 
column,  a  hot  water  boiler  should  be  selected  of  such  rated 
capacity  as  to  include  the  loss  from  the  mains  and  risers. 
Since  this  loss  is  usually  taken  from  20  to  30  per  cent.,  de- 
pending upon  the  thoroughness  with  which  the  basement 
mains  are  insulated,  the  heater  for  this  house  should  have 
a  rated  capacity  of  not  TCSS  than  720  square  feet  of  radiation. 


HOT    WATER   AND    STEAM    HEATING 
TABLE  XII. 


127 


1 

fe 

Radiators 
installed 

Lengths 
of  rad'or 
installed 

Riser 
sizes 

11 

'-1  a 

-H 

Sif 

"8 

1 

s 

°g 
•033 

eS  S 

£ 

rt  o 

<U  o 

Mis 

r 

1 

a 

o 

1 

3 

0 

to 

Sitting  R  

14000 

84 

15-32-3 

14-44-3 

84 

42 

\% 

VA 

IX 

Dining  R. 

10800 

14-26-3 

18-26-3 

32 

54 

m 

ji/ 

IX 

Study 

13250 

80 

82-14-8 

20-14-F 

72 

60 

V4 

1%, 

Kitchen..  

11900 

70 

12-32-3 

8  -45-4 

24 

I1/? 

IK 

\1A 

Rec'p'n  Hall  ... 

14000 

84 

15-32-3 

14-44-8 

34 

42 

VA 

Chamber  1  

9400 

57 

13-26-3 

16-26-3 

30 

48 

1% 

1% 

l% 

Chamber  2  

9850 

60 

13-26-3 

16-26-3 

80 

48 

W 

IX 

IX 

Chambers  

6600 

40 

10-26-3 

12-26-3  ' 

23 

36 

1 

1 

1 

Chamber  4  

5600 

35 

10-26-3 

12-26-3 

m 

36 

1 

1 

1 

Bath 

4400 

26 

6-26-3 

7-26-8 

14 

91 

1 

1 

1 

601 

HEATING    AND    VENTILATION 


27 —  6" 


^ i  IT 


FOUNDATION  PLAN. 
Ceiling   6'. 


HOT   WATER   AND    STEAM   HEATING  129 


FIRST    FLOOR   PLAN. 
Ceiling   10'. 

Fig.    66. 


130 


HEATING  AND  VENTILATION 


SECOND  FLOOR  PLAN. 
Ceiling  9'. 

Fig.    67. 


HOT    WATER   AND   STEAM   HEATING 


131 


12-26-3    7-26-3 


ExpTonK. 


lfe-26-3 
MAIN   AND    RISER   LAYOUT. 

Fig.    G7a. 


88.  Insulating  Steam  Pipes: — In  all  heating  systems, 
pipes  carrying  steam  or  water  should  be  insulated  to  protect 
from  heat  losses,  unless  these  pipes  are  to  serve  as  radiating 
surfaces.  In  a  large  number  of  plants  the  heat  lost  through 
these  unprotected  surfaces,  if  saved,  would  soon  pay  for  first 
class  insulation.  The  heat  transmitted  to  still  air  through 


132  HEATING  AND  VENTILATION 

one  square  foot  of  the  average  wrought  iron  pipe  is  from  2 
to  2.2  B.  t.  u.  per  hour,  per  degree  difference  of  temperature 
between  the  inside  and  the  outside  of  the  pipe.  Assuming 
the  minimum  value,  and  also  that  the  pipe  is  fairly  well 
protected  from  air  currents,  the  heat  loss  is,  with  steam  at 
100  pounds  gage  and  80  degrees  temperature  of  the  air, 
(338  —  80)  X  2  =  516  B.  t.  u.  per  hour.  With  steam  at  50,  25 
and  10  pounds  gage  respectively  this  will  be  436,  374  and  320 
B.  t.  u.  If  the  pipe  were  located  in  moving  air,  this  loss  would 
be  much  increased.  It  is  safe  to  say  that  the  average  low  pres- 
sure steam  pipe,  when  unprotected,  will  lose  between  350  and 
400  B.  t.  u.  per  square  foot  per  hour.  Taking  the  average  of 
these  two  values  and  applying  it  to  a  six  inch  pipe  100  feet 
in  length,  for  a  period  of  240  days  at  20  hours  a  day,  we  have 
a  heat  loss  of  171  X  375  X  240  X  20  —  307800000  B.  t.  u.  With 
coal  at  13000  B.  t.  u.  per  pound  and  a  furnace  efficiency  of  60 
per  cent,  this  will  be  equivalent  to  39461  pounds  of  coal, 
which  at  $2.00  per  ton  will  amount  to  $39.46.  From  tests 
that  have  been  run  on  the  best  grades  of  pipe  insulation,  it  is 
shown  that  80  to  85  per  cent,  of  this  heat  loss  could  be 
saved.  Taking  the  lower  value  we  would  have  a  financial 
saving  of  $31.56  where  the  covering  is  used.  Now  if  a  good 
grade  of  pipe  covering,  installed  on  the  pipe,  is  worth  $35.00, 
the  saving  in  one  year's  time  would  nearly  pay  for  the 
covering. 

To  re  effective,  insulation  should  be  porous  but  should 
be  protected  from  air  circulation.  Small  voids  filled  with 
still  air  make  the  best  insulating  material.  Hence,  hair 
felt,  mineral  wool,  eiderdown  and  other  loosely  woven  ma- 
terials are  very  efficient.  Some  of  these  materials,  however, 
disintegrate  after  a  time  and  fall  to  the  bottom  of  the  pipe, 
leaving  the  upper  part  of  the  ripe  comparatively  free.  Many 
patented  coverings  have  good  insulating  qualities  as  well  as 
permanency.  Most  patented  coverings  are  one  inch  in  thick- 
ness and  may  or  may  not  fit  closely  to  the  pipe.  A  good  ar- 
rangement is  to  select  a  covering  one  size  larger  than  the 
pipe  and  set  this  off  from  the  pipe  by  spacer  rings.  This 
air  space  between  the  pipe  and  the  patented  covering  is  a 
good  insulator  itself.  Table  45,  Appendix,  gives  the 
results  of  a  series  of  experiments  on  pipe  covering,  obtained 
at  Cornell  University  under  the  direction  of  Professor  Car- 
penter. These  values  are  probably  as  nearly  standard  as 
may  be  had.  (See  Art.  138  for  conduits.) 


HOT   WATER   AND   STEAM   HEATING  133 

80.  Water  Hammer: — «When  steam  is  admitted  to  a  cold 
pipe,  or  to  a  pipe  that  is  full  of  water,  it  is  suddenly  con- 
densed and  causes  a  sharp  cracking  noise.  The  concussion 
produced  by  this  condensation  may  become  so  severe  as  to 
crack  the  fittings  and  open  up  the  joints.  The  noise  is  due  to 
a  sudden  rush  of  water  in  an  endeavor  to  fill  the  vacuum 
produced  by  the  condensed  steam.  Steam  at  atm/ospheric 
pressure  occupies  1644  times  the  volume  of  the  water  that 
formed  it,  hence,  by  suddenly  condensing  it,  a  very  high 
vacuum  may  be  produced.  This  action  causes  a  relatively 
high  velocity  in  any  body  of  water  adjacent  to  it.  The 
worst  condition  is  found  when  a  quantity  of  steam  enters 
a  pipe  filled  with  water.  Condensation  suddenly  takes  place 
and  the  two  bodies  of  water  come  together  with  high  ve- 
locity causing  severe  concussion.  Steam  should  always  be 
admitted  to  a  cold  pipe,  or  to  one  filled '  with  water,  very 
slowly. 

90.  Returning  the  Water  of  Condensation,  In  a  Low 
Pressure  Steam  Heating  System,  to  the  Boiler: — In  re- 


Fig.    68.  Fig.  69. 

turning  the  water  of  condensation  to  the  boiler  four  methods 
are  in  use;  gravity,  steam  traps,  steam  loops  and  steam  or 
electric  pumps.  The  gravity  system  is  the  simplest  and  is  used 
in  all  cases  where  the  radiation  is  above  the  level  of  the 
boiler  and  where  the  boiler  pressure  is  used  in  the  mains. 
In  a  gravity  return,  no  special  valves  or  fittings  are  neces- 
sary, but  a  free  path  with  the  least  amount  of  friction  !n  It 
is  provided  between  the  radiators  and  a  point  on  the  boiler 
below  the  water  line.  No  traps  of  any  kind  should  be 
placed  in  this  return  circuit. 

All  radiation  should  be  placed  at  least  18  inches  above 
the  water  line  of  the  boiler  to  insure  that  the  water  will 
not  back  up  in  the  return  line  and  flood  the  lower  radiators. 


134  HEATING  AND  VENTILATION 

This  flooding  is  usually  the  result  of  a  restricted  steam  main. 
When  the  radiation  is  below  the  water  line,  or  where  the 
pressure  in  the  mains  is  less  than  that  in  the  boiler,  some 
form  of  steam-trap  or  motor  pump  must  be  put  in  with  special 
provision  for  returning  this  water  to  the  boiler.  Two  kinds 
of  traps  may  be  had,  low  pressure  and  high  pressure.  The 
first  is  well  represented  by  the  bucket  trap,  Fig.  68,  and  the 
second,  by  the  Bundy  trap,  Fig.  69.  The  action  of  these  traps 
is  as  follows.  Bucket  trap. — Water  enters  at  D  and  collects 
around  the  bucket,  which  is  buoyed  up  against  the  valve. 
The  water  collects  and  overflows  the  bucket  until  the  com- 
bined weight  of  the  water  and  bucket  overbalances  the 
buoyancy  of  the  water.  The  bucket  then  drops  and  the 
steam  pressure  upon  the  inside,  acting  upon  the  surface  of 
the  water,  forces  it  out  through  the  valve  and  central  stem 
to  the  outlet  B.  When  a  certain  amount  of  this  water  has 
been  ejected,  the  bucket  again  rises  and  closes  the  valve. 
This  action  is  continuous.  Bundy  trap. — Water  enters  at  D 
through  the  central  stem  and  collects  in  the  bowl  A,  which 
is  held  in  its  upper  position  by  a  balanced  weight.  When 
the  water  collects  in  the  bowl  sufficiently  to  lift  the  weight, 
the  bowl  drops,  the  valve  E  opens,  and  steam  is  admitted 
to  the  bowl,  thus  forcing  the  water  out  through  the  curved 
pipe  and  the  valve  E.  This  action  is  continuous. 

Each  trap  is  capable  of  lifting  the  water  approximately 
2.4  feet  for  each  pound  of  differential  pressure.  Thus,  for  a 
pressure  of  5  pounds  gage  within  the  boiler  and  2  pounds 
gage  on  the  return,  the  water  may  be  lifted  7  feet  above 
the  trap,  or  say,  to  the  top  of  an  ordinary  boiler.  This  is  not 
sufficient,  however,  to  admit  the  water  into  the  boiler 
against  the  pressure  of  the  steam.  A  receiver  should  be 
placed  here  to  catch  the  water  from  the  separating  trap 
and  deliver  it  to  a  second  trap  above  the  boiler  which,  in 
turn,  feeds  the  boiler.  Live  steam  is  piped  from  the  boiler 
to  each  trap,  but  the  steam  supply  to  the  lower  trap  is 
throttled,  to  give  only  enough  pressure  to  lift  the  water 
into  the  receiver.  A  system  connected  up  in  this  way  is 
shown  in  Fig  70.  Traps  which  receive  the  water  of  con- 
densation for  the  purpose  of  feeding  the  boiler  are  called 
return  traps  and  sometimes  work  under  a  higher  pressure 
of  steam  than  the  separating  traps.  Many  different  kinds 
of  traps  are  in  general  use  but  these  will  illustrate  the 
principle  of  returning  the  condensation  to  the  boiler. 


HOT    WATER   AND    STEAM   HEATING 


135 


TO  ASH  PIT 

Fig.   70. 


A  very  simple  arrange- 
ment, and  yet  a  very  difficult 
one  to  operate  satisfactorily, 
is  by  the  use  of  the  steam  loop, 
Fig.  71.  The  water  of  con- 
densation from  the  radiators 
drains  to  the  receiver  A, 
which  is  in  direct  communi- 
cation with  the  riser  B.  The 
drop  leg-  D,  being  in  com- 
munication with  the  boiler 
through  a  check  valve  which 
opens  toward  the  boiler  at 
the  lowest  point,  is  filled 
with  water  to  the  point  X, 
.sufficiently  high  above  the 
water  line  of  the  boiler  that 
the  static  head  balances  the  differential  pressure  between  the 
steam  in  the  boiler  and  that  in  the  condenser.  The  horizon- 
tal run  of  pipe  C  serves  as  a  condenser  jind,  in  producing  a 
partial  vacuum,  lifts  the  water  from  the  receiver.  This 
water  is  not  lifted  as  a  solid  body,  but  as  s-'ugs  of  water 
interspersed  with  quantities  of  steam  and  vapor.  The  water 
in  A  is  at  or  near  the  boiling  point  and  the  reduced  pressure 
in  B  reevaporates  a  portion  of  it  which,  in  rising  axa  a 
vapor,  assists  in  carrying  the  rest  of  the  water  over  the 
goose-neck.  When  the  condensation  in  D  rises  above  the 
point  X,  the  static  pressure  overbalances  the  differential 
steam  pressure,  and  water  is  fed  to  the  boiler  through  the 
check. 

To  find  the  location  of  the  point  X,  above  the  water  line 
in  the  boiler,  the  following  will  illustrate.  Let  the  pres- 
sures in  the  boiler,  condenser  and  receiver  be  respectively 
5,  2  and  4  pounds  gage,  then  the  differential  pressure  between 
the  boiler  and  condenser  is  3  pounds  per  square  inch.  If  the 
weight  of  one  cubic  foot  of  water  at  212  degrees  is  59.76 
pounds,  then  the  pressure  is  .42  pounds  per  square  inch  for 
each  foot  in  height.  Stated  in  other  words,  one  pound  dif- 
ferential pressure  will  sustain  2.4  feet  of  water.  With  a 
pressure  difference  of  3  pounds,  this  gives  3  -f-  .42  =  7.2 
feet  from  the  water  level  in  the  boiler  to  the  point  X,  not 
taking  into  account  the  friction  of  the  piping  and  check 
Which  would  vary  from  10  to  30  per  cent.  Assuming  this 


136 


HEATING  AND  VENTILATION 


friction  to  be  20  per  cent,  we  have  7.2  -i-  .80  =  9  feet  of  head 
to  produce  motion  of  the  water. 

The  length  of  the  riser  pipe  B  and  its  diameter,  depend 
upon  the  differential  pressure  between  the  condenser  and 
the  receiver,  and  upon  the  rapidity  of  condensation  in  the 
horizontal. 

With  a  differential  pressure  of  2  pounds  this  would  sus- 
pend 2  X  2.4  =  4.8  feet  of  solid  water.  The  specific  gravity, 
however,  of  the  mixture  in  this  pipe  is  much  less  than  that 
of  solid  water.  For  the  sake  of  argument  let  this  specific 
gravity  be  20  per  cent,  of  that  of  solid  water,  then  we  would 


Fig.   71. 

have  a  possible  lift,  not  including  friction,  of  5  X  4.8  =  24 
feet.  This  is  24  —  9  =  15  feet  below  the  water  level  in  the 
boiler.  The  diameter  of  the  riser  may  vary  for  different 
plants,  but  for  any  given  plant  the  range  of  diameters  is 
very  limited.  These,  as  has  been  stated,  are  usually  found 
by  experiment. 

A  drain  cock  should  be  placed  in  the  receiver  at  the 
lowest  point.  When  cold  water  has  collected  in  the  re- 
ceiver it  is  necessary  to  drain  this  water  to  the  sewer  before 
the  loop  will  work.  An  air  valve  should  be  placed  at  the  top 
of  the  goose-neck  to  draw  off  the  air.  If  the  horizontal  pipe 
is  filled  with  air,  there  will  be  no  condensation  and  the  loop 
will  refuse  to  work.  Never  connect  a  steam  loop  to  a  boiler 


HOT   WATER   AND    STEAM   HEATING 


137 


in  connection  with  a  pump  or  any  other  boiler  feeder.  To 
determine  whether  a  loop  is  working  or  not,  place  the  hand 
on  the  horizontal  pipe.  If  this  is  cold  it  is  not  working. 

The  last  method  mentioned  for  feeding  condensation  to 
the  boiler  was  by  the  use  of  a  steam  or  electric  pump.  The 
operation  of  the  steam  pump  is  fully  discussed  in  Airt.  92. 
An  electric  motor-pump  with  its  receiver  and  pipe  connec- 
tions is  shown  in  Fig.  72.  Its  operation  is  very  similar  to 
that  of  the  steam  pump.  When  the  returning  condensation 


^EQUALIZING 
PIPE 

1 

-ja 

r 

• 

RECEIVER 

BELOW     LOWEST 
RADIATION 

n       n 

u 

Fig.   72. 

fills  the  receiver  to  a  certain  point  a  float  regulator  starts 
the  motor  and  pumps  the  water  from  the  receiver  to  the 
boiler.  When  the  water  level  drops  the  operation  is  re- 
versed and  the  pump  is  automatically  stopped.  The  motor 
pump  is  used  especially  on  low  pressure  heating  systems 
W'here  the  water  of  condensation  from  the  coils  and  radia- 
tors drains  below  the  boiler.  If  the  boiler  pressure  were 
high  then  the  ordinary  steam  pump  would  be  used.  W'here 
the  pressure  within  the  boiler,  however,  Is  near  that  in  the 
return  main  the  operation  of  such  a  piece  of  apparatus  is 
less  expensive  than  that  of  the  steam  pump. 

91.  Suggestions  for  Operating  Hot  Water  Heaters  and 
Steam  Boilers: — Before  firing  up  in  the  morning,  examine 
the  pressure  gage  to  see  if  the  system  is  full  of  water.  If 
there  be  any  doubt,  inspect  the  water  level  in  the  expan- 
sion tank.  If  it  is  a  steam  system,  examine  the  gage  glass 
and  try  the  cocks  to  see  if  there  is  sufficient  water  in  the 
boiler. 


138  HEATING  AND  VENTILATION 

See  that  all  valves  on  the  water  lines  are  open.  On  the 
steam  system,  try  the  safety  valve  to  make  sure  that  It  Is 
free.  Also  see  if  the  pressure  gage  stands  at  zero. 

Clean  the  fire  and  sprinkle  over  it  a  small  amount  of 
fresh  coal. 

Open  up  the  drafts  and  when  the  fire  is  burning  well 
fill  up-  with  coal. 

In  starting  a  fire  under  a  cold  boiler  it  should  not  be 
forced,  but  should  warm  up  gradually. 

Hard  coal  may  be  thrown  evenly  over  the  fire.  Soft  coal 
should  be  banked  in  front  on  the  grate,  until  the  gases  are 
driven  off.  It  is  then  distributed  back  over  the  fire. 

The  thickness  of  the  fire  will  vary  from  four  inches  to 
one  foot  depending  upon  the  draft  and  the  kind  of  coal. 

Clean  the  fire  when  it  has  burned  low,  partially  closing 
the  drafts  while  cleaning. 

In  a  boiler  or  heater,  using  the  water  over  continuously, 
there  will  be  little  need  of  cleaning  out  the  inside.  In  a 
system  using  fresh  water  continuously,  however,  the  boiler 
should  be  blown  off  and  cleaned  about  once  or  twice  a  month. 
Never  blow  off  a  boiler  while  hot  or  under  heavy  pressure. 

In  every  system  the  heater  or  boiler  should  be  thoroughly 
overhauled  and  cleaned  before  firing  up  in  the  fall. 

Keep  the  ash  pit  clean  and  protect  the  grates  from  burn- 
ing out. 

Keep  the  tubes  and  gas  passages  clean  and  free  from  soot. 

Inspect  the  pressure  gage,  glass  gage,  water  cocks  and 
thermometers  frequently. 

In  case  of  low  water  in  a  steam  system,  cover  the  fire 
with  wet  ashes  or  coal  and  close  all  the  drafts.  Do  not 
open  the  safety  valve.  Do  not  feed  water  to  the  boiler.  Do 
not  draw  the  fire.  Keep  the  conditions  such  as  to  avoid  any 
sudden  shock.  After  the  steam  pressure  has  dropped,  draw 
the  fire. 

Excessive  pressure  may  be  caused  by  the  sticking  of  the 
safety  valve  in  the  steam  system,  or  by  the  stoppage  of  the 
water  line  to  the  expansion  tank  in  the  hot  water  system. 
The  safety  valve  should  never  be  allowed  to  lime  up,  and  the 
expansion  tank  should  always  be  open  to  the  heater  and  to 
the  overflow. 

When  leaving  the  fires  for  the  night,  push  them  to  the 
rear  of  the  grate  and  bank  them  as  stated  in  Art,  59. 


HOT   WATER  AND   STEAM   HEATING  139 

References  on  Hot  Water  and  Steam. 

TECHNICAL  BOOKS. 

Snow,  Principles  of  Heat.,  Chap.  IX,  X.  I.  C.  S.,  Prin.  of  Heat 
and  Vent.,  p.  1185,  1091.  Monroe,  Steam  Heat.  &  Vent.,  p.  13. 
Lawler,  Hot  Water  Heating,  p.  19.  Carpenter,  Heat.  &  Vent.  Bldgs., 
pp.  150,  231.  Thompson,  House  Heat.  &y  Steam  &  Water,  p.  15. 
Hubbard,  Power,  Heat.  &  Vent.,  pages  433,  464,  484,  505,  510. 

TECHNICAL   PERIODICALS. 

Engineering  News.  Suggestions  for  Exh'st  Steam  Heat, 
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53,    No.    9,    Nov.    26,    1910.       Proportions    and    Power    of    Low 
Pressure   Heating   Boilers,   Vol.    47,    No.    11,   June    12,    1909.    p. 
319.     How  to  Install!  and  Cover  a  Steam  or  Hot  Water  Main, 
"Phoenix,"   Vol.    46,   No.    10,   March    6,    1909,   p.    278.     How   to 


140  HEATING  AND  VENTILATION 

Secure  Correct  Pipe  Sizes  for  Low  Pressure  Steam  Heating, 
E.  K.  Monroe,  Vol.  45,  No.  9,  Nov.  28,  1908,  p.  243.  Rules  for 
Proportioning  Indirect  Heating  Plants,  R.  T.  Crane,  Vol.  49, 
No.  6,  Nov.  6,  1909,  p.  143.  Trans.  A.  8.  H.  &  V.  E.  Circulation 
of  Hot  Water,  J.  S.  Brennan,  Vol.  XI,  p.  93.  Residence  Heat- 
ing by  Direct  and  Indirect  Hot  Water,  E.  F.  Capron,  Vol. 
XI,  p.  174.  Standard  Sizes  of  Steam  Mains,  J.  A.  Donnelly, 
Vol.  XIII,  p.  43.  The  Carrying  Capacity  of  Pipes  in  Low 
Pressure  Steam  Heating,  Wm.  Kent,  Voil.  XIII,  p.  54.  Heat- 
Ing  and  Ventilating  a  Group  of  Public  Schools,  S.  R.  Lewis, 
Vol.  XIII,  p.  187.  The  Combined  Pressure  and  Vacuum  Sys- 
tems of  Steam  Heating,  G.  Hoffman,  Vol.  XIII,  p.  223.  Sizes 
of  Return  Pipes  in  Steam  Heating  Apparatus,  J.  A.  Donnelly, 
Vol.  XII,  p.  109.  Proportioning  Hot  Wiater  Radiation  in 
Combination  Systems  of  Hot  Water  and  Hot  Air  Heating, 
R.  C.  Carpenter,  Vol.  VII,  p.  132.  Tests  of  Radiators  with 
Superheated  Steam,  R.  C.  Carpenter,  Vol.  VII,  p.  206.  Rela- 
tive Economy  of  Steam,  Vapor,  Vacuum  and  Hot  Water 
Heating  for  Residences,  Vol.  XII,  p.  341.  The  Relation  be- 
tween the  Completeness  of  Air  Removal  and  the  Efficiency 
of  Steam  Radiators,  Vol.  XII,  p.  315.  Measurements  of  Wall 
Radiators,  V01.  XII,  p.  361.  Advantages  of  Standard  Dimen- 
sions of  Radiator  Valves  and  Connections,  Vol.  XIII,  p.  145. 
The  Relative  Healthfulness  of  Direct  and  Indirect  Heat- 
ing Systems,  Vol.  XIII,  p.  136.  Improving  the  Heating 
Capacity  of  a  Radiator  by  an  Electric  Fan,  Vol.  VIII,  p.  222. 
Engineering  Record.  Mechanical  Plant  of  the  Harvard 
Medical  School,  No.  2,  Aug.  7,  1909.  Mechanical  Equipment 
of  the  Hotel  LaSalle,  Chicago,  Sept.  11,  1909.  Mechanical 
Plant  of  the  Washington  Municipal  Bldg.,  Oct.  30,  1909. 
Heating  and  Ventilation  of  the  Museum  of  Fine  Arts,  Bos- 
ton, Nov.  13,  1909.  Heating  Plant  for  a  Railway  Storehouse, 
Dec.  18,  1909.  Heating  and  Ventilation  of  the  Hotel  Plaza, 
N.  T.,  Mar.  13  and  Mar.  20,  1909.  Central  Heating  and 
Lighting  Plant  for  the  United  States  Military  Academy,  May 
1,  May  8  and  May  15,  1900.  Electric  Railway  Journal.  Heating 
System  in  Car  House  of  Toronto  &  York  Radial  Rail- 
way, March  26,  1910,  p.  543.  The  Elevated  Shops  and  Ter- 
minals of  the  Brooklyn  Rapid  Transit  Co. — Organization  and 
General  Layout  -at  East  New  York,  Feb.  2,  1907,  p.  170.  The 
Elevated  Shops  and  Terminals  of  the  Brooklyn  Rapid  Tran- 
sit Co.— The  Thirty-sixth  St.  Inspection  Plant,  March  9,  1907, 
p.  406.  The  Metal  Worker.  Unstable  Water  Lines  in  Steam 
Boilers,  March  26,  1910,  p.  429.  Air  Venting  Hot  Water  Sys- 
tems, June  4,  1910,  p.  755.  Heating  Swimming  Pool,  June  25, 
1910,  p.  854.  Air  Venting  Steam  Systems,  July  9,  1910,  p.  30 
Heating  and  Ventilating  Six  Room  School  Building,  Oct.  23 
1909,  p.  45.  Steam  Heating  in  a  Cottage,  July  11,  1908,  p. 
45.  Indirect  Hot  Water  Heating  in  Residence,  Oct.  24,  1908, 
p.  43.  Hot  Water  Heating  in  a  Factory  in  Hoboken.  N.  J., 
April  4,  1908,  p.  39.  Power.  Economics  of  Hot  Water  Heating, 
Ira  N.  Evans,  Sept.  12,  1911.  Hot  Water  Heating  for  Institu- 
tions, Ira  N.  Evans,  May  14,  1912.  Forced  Circulation  in  Hot 
Wkter  Heating,  Charles  L.  Hubbard,  Dec.  20,  1912;  Nov.  15, 
1912. 


CHAPTER   IX. 


MECHANICAL    VACUUM,    STEAM    HEATING    SYSTEMS. 


92.  In  Addition  to  the  Brief  Discussion  of  vacuum  steam 
heating  as  found  in  Art.  69,  it  will  be  well  to  discuss 
more  in  detail  the  various  systems  by  which  this  heating  is 
accomplished.  The  advantages  to  be  derived  by  the  positive 
withdrawal  of  the  air  and  the  condensation  from  the  radi- 
ators and  pipes,  compared  to  the  natural  circulation  of  the 
gravity  system,  are  now  too  well  established  to  need  much 
discussion.  Mains  and  returns  that  are  too  small,  horizontal 
runs  of  piping  that  are  unevenly  laid  so  as  to  form  air  and 
water  pockets,  radiators  that  are  only  partially  heated  be- 
cause of  the  entrapped  air,  leaking  air  and  radiator  valves, 
radiators  partially  filled  with  condensation  and  all  the  accom- 
panying cracking  and  pounding  throughout  many  of 
the  gravity  systems,  are  sufficient  causes  to  de- 
mand a  cure,  if  such  cure  can  be  found.  One  should  not 
understand  by  this  statement  that  every  mechanical  vacuum 
system  is  a  cure  for  all  the  ills  in  the  heating  work,  for  even 
these  systems  may  be  improperly  designed.  The  steam  pipes 
may  be  too  small  to  supply  the  radiators,  although  smaller 
pipes  may  be  used  in  this  than  in  the  gravity  work,  the 
valves  may  be  defective,  or  the  vacuum  specialties  may  be 
inefficient.  Most  of  the  defects  in  the  average  plant,  however, 
are  because  of  imperfections  in  that  part  of  the  system 
from  the  radiator  to  the  boiler,  and  all  of  the  first  class 
vacuum  systems  are  planned  to  meet  just  these  conditions. 

Vacuum  systems  have  other  advantages  over  the  gravity 
work,  the  principal  one  being  that  of  lifting  the  return  con- 
densation to  a  higher  level.  This  is  noticeable  in  the  plac- 
ing of  radiators  or  coils  in  basement  rooms.  Another  very 
important  advantage  is  in  the  laying  out  of  the  heating  coils 
for  shop  buildings  and  manufacturing  plants.  Low  pres- 
sure gravity  coils  are  limited  to  a  length  of  about  75  feet. 
Usually  the  condensation  -in  a  long  coil  of  this  kind  is  very 
great  and  requires  extra  heavy  pressure  on  the  steam  end 
to  circulate  it.  The  steam  follows  the  line  of  least  resistance 


142 


HEATING  AND  VENTILATION 


and  forces  the  air  out  of  certain  pipes  and  permits  it  to  re- 
main in  others,  the  differential  pressure  not  being-  great 
enough  to  eliminate  all  the  air  and  heat  the  pipes  uniformly. 
As  a  result  of  these  conditions  some  of  the  pipes  remain 
cold  and  ineffective  as  prime  radiating-  surface.  A  vacuum 
system,  with  its  positive  circulation,  increases  the  differ- 
ential pressure,  removes  the  air  and  gives  uniform  heating- 
effect  in  coils  that  are  several  times  'as  long  as  can  be 
safely  supplied  by  the  gravity  system.  The  accumulation  of 
air  in  the  radiators  and  coils  is  especially  noticeable  in 
systems  using  exhaust  steam. 

When  exhaust  steam  from  engines  or  turbines  is  usecl 
in  a  gravity  heating-  system,  the  back  pressure  is  carried 
from  atmospheric  pressure  to  10  pounds  gage.  With  the  ap- 
plication of  the  vacuum  system  it  is  possible  to  maintain 
this  constantly  at  about  atmospheric  pressure.  It  is 
claimed  by  some,  that  it  is  possible  to  reduce  the  pressure 
in  the  radiators  to  such  a  degree  that  the  pressure  in  the 
supply  mains  will  fall  considerably  below  atmosphere.  No 
doubt  the  specialty  valves  may  be  set  so  as  to  do  this,  but 
it  would  scarcely  be  considered  an  economical  arrangement. 


BACK  PRESSURE 
VALVE 


Fig.   73. 


MECHANICAL    VACUUM    HEATING  143 

The  principal  features  of  a  mechanical  vacuum  system 
are  shown  in  Fig.  73.  Live  steam  is  conducted  to  the  engine 
and  to  the  heating  main,  the  latter  through  a  pressure  re- 
ducing valve  to  be  used  only  when  exhaust  steam  is  insuf- 
ficient. The  exhaust  steam  from  the  engines  and  pumps 
is  conducted  to  the  heating  main  and  to  the  feed  water 
h-eater.  The  exhaust  steam  line  opens  to  the  atmosphere 
through  a  back  pressure  valve  which  is  set  at  the  desired 
pressure  for  the  supply  steam.  An  oil  separator  shown  on 
the  exhaust  steam  line  removes  the  oil  and  delivers  it  to  an 
oil  trap.  At  the  entrance  to  the  feed  water  heater,  the 
exhaust  steam  passes  through  a  series  of  baffle  plates  which 
remove  the  oil  and  entrained  water  from  that  part  of  the 
steam  which  enters  the  heater.  A  boiler  feed  pump  and  a 
vacuum  pump,  with  the  attending  valves  and  governing  ap- 
pliances, complete  the  power  room  equipment.  The  steam 
supply  to  the  heating  system  is  piped  to  radiators  and  coils 
in  the  ordinary  way,  with  or  without  temperature  control. 
A  thermostatic  valve,  or  patented  motor  valve,  is  placed  at 
the  return  end  of  each  radiator  and  coil  and  these  returns 
are  then  brought  together  in  a  common  return  which  leads 
to  a  vacuum  pump  or  ejector.  The  return  pipe  and  specialty 
valve  for  any  one  unit  is  usually  l/2  inch.  The  combined  re- 
turn increases  in  size  as  more  radiation  is  taken  on.  Hori- 
zontal steam  mains  usually  terminate  in  a  drop  leg  Whiclh  is 
tapped  to  the  return  8  to  15  inches  above  the  bottom  of  the 
leg.  Each  rise  in  the  system  has  a  drop  leg  at  the  lower 
end  of  the  rise.  These  points  and  all  other  points  where 
condensation  may  collect  are  drained  through  specialty 
valves  to  the  return.  Water  supply  systems  may  be  tapped 
for  steam  and  return  condensation  the  same  as  any  ordi- 
nary radiator.  Steam  is  carried  in  the  main  at  about  at- 
mospheric pressure,  and  just  enough  vacuum  is  maintained 
on  the  return  to  insure  positive  and  noiseless  circulation. 
In  many  cases  wliere  special  lifts  are  required,  these  return 
systems  are  run  under  a  negative  pressure  of  6  to  10  inches 
of  mercury.  Under  such  conditions  water  may  be  lifted 
fram  6  to  10  feet.  Either  closed  or  opened  feed  water 
heaters  may  be  used  with  the  layout  as  given.  (For  com- 
parative sizes  of  gravity  and  vacuum  returns  see  Table  38, 
Appendix.) 

Fig.  74  shows  a  section  through  the  Marsh  vacuum  pump 
which  represents  a  type  very  generally  used  in  this  work. 


144 


HEATING  AND  VENTILATION 


It  will  be  noticed  that  this  pump  has  a  steam  operated  valve. 
The  automatic  governing  feature  of  this  valve  tends  tc 

equalize  the  cylinder 
pressure  to  meet  the 
varying  resistance  in 
the  main  return  of  the 
heating  system.  Such 
a  pump  is  handling  al- 
ternately solid  water 
and  vapors,  hence 
there  is  great  tenden- 
cy of  the  ordinary 
pump  to  race  and 
pound  at  such  times. 
In  its  operation  the 
steam  enters  at  A  and 
passes  into  the  space 
B  through  the  annu- 
lar opening  C  be- 
Fig.  74.  tween  the  reduced 

neck  of  the  valve  and 

the  bore  o»f  the  first  chest  wall.  It  is  thus  projected  against 
the  inside  surface  of  the  valve  head  before  entering  into 
the  port  and  passing  to  the  cylinder.  On  reaching  the 
cylinder  and  driving  the  piston  to  the  right,  the  reaction  of 
the  steam  through  port  D  to  the  opposite  side  of  the  valve 
head,  tends  to  further  open  the  steam  port  C.  The  valve 
then  holds  a  position  depending  upon  the  relative  strength 
of  the  forces  which  tend  to  move  it  in  opposite  directions, 
i.  e.,  admission  steam  which  tends  to  close  the  valve,  and  the 
cylinder  steam  which  tends  to  open  the  valve.  This  is 
the  governing  feature.  It  will  be  noticed  that  the  pump 
piston  is  in  two  parts  and  carries  steam  at  admission  pres- 
sure upon  the  inside.  This  steam  is  admitted  along  the 
dotted  line  to  the  center  of  the  cylinder  head,  thence  through 
a  small  tube  and  packing  box  to  the  hollow  piston  rod, 
which  has  a  direct  connection  with  the  center  of  the  piston. 
When  the  piston  has  moved  sufficiently  to  bring  the  central 
space  E  in  line  with  the  duct  D,  .steam  is  admitted  to  the 
right  of  the  piston  valve  thus  forcing  it  back,  cutting  off 
the  steam  at  C,  opening  up  the  exhaust  to  the  atmosphere 
through  F  and  admitting  steam  to  the  other  end  o«f  the 
cylinder.  The  action  is  thus  reversed  and  continuous.  Ejec- 


MECHANICAL    VACUUM    HEATING 


145 


tors  operated  by  steam,  water  and  electricity  are  also  used 
to  produce  a  vacuum.  No  comparison  is  made  here  of  t'he 
various  systems  of  producing  vacuum  since  each  gives  satis- 
faction when  properly  installed.  In  each  case  there  is  a 
loss  of  energy  but  this  loss  is  amply  repaid  in  the  added 
benefits. 

Several  patented  systems  of  mechanical  vacuum  heating 
are  now  upon  the  market.  These  are  in  large  measure  an 
outgrowth  of  the  original  Williames  System,  patented  in 
1882.  Each  .system  is  well  represented  by  the  above  diagram 
in  all  particulars  concerning  the  steam  and  water  circu- 
lation. The  chief  difference  between  them  is  in  the  t'hermo- 
static  or  motor  connection  at  the  entrance  to  each  individual 
return. 

93.  Webster  System: — In  this  system  a  pump  is  used  to 
produce  the  vacuum.  A  special  fitting,  called  a  water-seal 
motor,  or  thermostatic  valve,  is  used  on  all  radiators,  coils  and 
drainage  points.  Fig.  75  &how,s  a  section  of  one  of  the  motor 
valves.  Other  models  are  constructed  so  as  to  have  the  out- 
let in  a  horizontal  direction,  either  parallel  with  or  90  de- 
grees to  the  inlet.  Fig.  76  shows  an  application  of  this  to  a 
radiator  or  coil.  The  dirt  strainer  is  usually  placed  between 
the  radiator  or  coil  and  the  motor  valve.  This  strainer 


Fig.  75. 


Fig.  76. 


collects  the  dirt  and  protects  from  clogging  the  motor  valve. 
C  attaches  to  the  return  end  of  the  radiator  or  coil  and  L 
leads  to  the  vacuum  pumip.  O  is  the  central  tube,  the  lower 
end  of  which  is  a  valve.  A  is  a  hollow  cylindrical  copper 
float,  the  central  tube  of  which  fits  loosely  over  spind'le  B. 


146 


HEATING  AND  VENTILATION 


The  function  of  the  cylinder  A  is  to  raise  the  tube  G  from 
the  seat  H  and  open  the  discharge  to  the  pump.  Ordinarily, 
the  float  is  down  and  the  central  tube  valve  is  resting  upon 
the  seat  and  cuts  off  communication  with  the  radiator,  ex- 
cepting as  air  may  be  drawn  from  the  radiator  down  the 
central  tube  around  the  spiral  plug.  The  water  of  conden- 
sation accumulating  in  the  radiator  or  coil  passes  into  the 
chamber  E,  sealing  the  valve,  and  when  sufficient  water  has 
accumulated  to  lift  the  float,  it  opens  a  passageway  for  a 
certain  amount  of  the  water  to  be  withdrawn  to  the  return. 
When  this  water  becomes  lowered  sufficiently,  the  valve 
again  seats  itself  and  the  cycle  is  completed.  This  action 
continues  as  long  as  water  is  present  in  the  radiator.  These 
motor  valves  are  made  of  three  sizes,  %  inch,  %  inch  and  1 
inch.  The  first  is  the  standard  size  and  has  a  capacity  of 
approximately  200  feet  of  radiation. 

Fig.  77  shows  thermostatic  valves.  It  will  be  seen  that 
the  automatic  feature  in  a  is  the  compound  rubber  stalk, 
which  expands  and  contracts  under  heat  and  cold.  The 


Fig.  77. 

adjusting  screw  at  the  top  permits  the  valve  to  be  set  for 
any  conditions  of  temperature  and  pressure  within  the  radi- 
ator. The  water  of  condensation  passes  through  a  screen 
and  comes  in  contact  with  the  rubber  stalk.  The  tempera- 
ture of  the  water  being  less  than  that  of  steam  the  stalk 
contracts  and  the  water  is  drawn  through  the  opening  A  by 
the  action  of  the  pump.  As  soon  as  the  water  has  been  re- 


MECHANICAL    VACUUM    HEATING 


147 


moved,  steam  flows  around  the  stalk  and  expands  until  it 
closes  the  seat.  This  process  is  a  continuous  one  and  auto- 
matically removes  the  water  from  the  radiator.  The  screen 
serves  the  purpose  of  the  dirt  strainer  as  mentioned  above. 
Fig.  77,  6,  shows  a  sylphon  arrangement  where  the  movement 
of  the  valve  is  obtained  by  the  expansion  and  contraction  of 
the  fluid  inside  the  bellows. 

A  suction  strainer,  which  is  very  similar  to  the  dirt  strain- 
er only  larger  in  capacity,  is  placed  upon  the  return  line 
next  the  pump.  This  fitting  usually  has  a  cold  water  con- 
nection to  be  used  at  times  to  assist  in  producing  a  more 
perfect  vacuum.  The  piping  system  for  the  automatic  con- 
trol of  the  vacuum!  pump  is  shown  in  Fig.  78.  It  will  be 
seen  that  the  vacuum  in  the  re- 
turn operates  through  the  gover- 
nor to  regulate  the  steam  supply 
to  the  pump  cylinder,  thus  con- 
trolling the  speed  of  the  pump. 
Occasionally  it  is  desirable  to 
have  certain  parts  of  the  heating 
system  under  a  different  vacuum. 
An  Illustration  of  this  would  be 
where  the  radiators  within  the 
building  were  run  under  a  neg- 
ative pressure  of  about  one 
pound,  and  a  set  of  heating  coils 
in  the  basement  were  to  be  carried  under  a  negative  pressure 

of  four  pounds.  The  Web- 
ster System,  type  D,  Fig. 
79,  imieets  this  condition. 
The  exact  difference  be- 
tween the  suction  pressure 
and  the  pressure  in  the 
radiators  can  be  varied  to 
suit  any  condition  by  the 
controller  valve.  A  trap 
and  a  controller  valve 
should  be  applied  to  each 
line  having  a  different 


79. 


pressure  from  that  in  the  suction  line. 

A  modulation  valve,  for  graduating  the  steam  supply  to  the 
radiator,  has  been  designed  by  this  Company  and  may 
be  applied  to  any  Webster  Heating  System  to  assist  in  its 


148 


HEATING  AND  VENTILATION 


regulation.  This  modulation  valve  serves  to  graduate  the 
steam  supply  to  the  radiators  so  that  the  pressure  may  be 
maintained  at  any  point  to  suit  the  required  heat  loss  from 
the  building. 

94.  VanAuken  System: — In  this  system,  as  in  the  pre- 
vious one,  the  vacuum  in  the  return  main  is  produced  by  a 
vacuum  pump  wthich  is  controlled  by  a  specially  designed 
governor.  The  automatic  valves  which  are  placed  on  the 
radiators,  coils  and  other  drainage  points  along  the  system, 
are  called  Belvac  Thermofiers,  and  are  shown  in  section  by 
Fig.  80.  This  valve  is  automatic  and  removes  the  water  of 
condensation  by  the  controlling  ac- 
tion of  a  float.  It  is  connected  to  the 
radiator  or  coil  at  K  and  to  the  vacu- 
um return  pipe  at  L.  The  water  of 
condensation  is  drawn  through  the 
|.A  return  pipe  into  chamber  D  until  it 
reaches  the  inverted  weir  E  which 
gives  it  a  water  seal.  It  is  thence 
drawn  upward  into  space  D  until  it 
overflows  into  the  float  chamber  AA, 
where  it  accumulates  until  the  line 
of  flotation  is  reached.  When  the 
float  C  lifts,  the  valve  seat  at  B 
opens  and  allows  the  waler  to  es- 
cape into  the  vacuum  return  pipe. 
After  the  removal  of  the  water  the  float  again  settles  on  seat 
B  until  sufficient  water  accumulates  in  the  float  chamber  to 
again  lift  it,  when  the  cycle  is  repeated. 

The  air  contained  in  the  radiators  or  coils  is  drawn 
through  the  return  and  up  through  chamber  D  into  the  top 
of  the  float  chamber.  Here  its  direction  follows  arrows  Q  G, 
being  drawn  through  the  small  opening  in  the  guide-pin  at 
F,  down  through  the  hollow  body  of  the  copper  float  and 
valve  seat  B,  into  the  vacuum  return.  This  removal  of  air  is 
continuous  regardless  of  the  amount  of  water  present.  The 
by-pass  1,  when  open,  allows  all  dirt,  coarse  sand  or  scale 
to  pass  directly  into  the  vacuum  return,  thus  cleaning  the 
valve.  By  opening  the  by-pass  /  only  part  way,  the  con- 
tents of  chamber  A  may  be  emptied  into  the  vacuum  return 
without  interfering  with  the  conditions  in  space  />.  The 
ends  of  the  float  are  symmetrical,  hence  it  will  work  either 
way.  The  thermoflers  are  made  in  four  standard  sizes  of 


Fig.   80. 


MECHANICAL    VACUUM    HEATING 


149 


outlets,  two  having  Vz  inch  and  two  having-  %  inch  outlets. 
These  valves  have  capacities  of  125,  300,  550  and  1200  square 
feet  of  radiation  respectively.  ;<  ., 

Drop  legs,  strainers,  governors  and  other  specialties 
usually  provided  by  such  companies  are  supplied  in  addition 
to  the  thermofiers.  When  a  differential  vacuum  is  to  be  ob- 
tained a  special  arrangement  of  the  piping  system  is  planned 
to  cover  this  point.  The  piping  connections  around  the  auto- 
matic pump  governor  are  the  same  as  are  shown  in  Fig.  78. 
95.  Automatic  Vacuum  System: — In  this  system  the 
automatic  vacuum  valve,  which  takes  the  ;place  of  the  motor 
valve  and  thermofier  in  the  two  preceding  systems,  is  shown 
in  Fig.  81.  K  is  the  entrance  to  the  radiator  and  L  to  the 

vacuum  return.  Screen  F 
prevents  scale  and  dirt 
from  entering  the  valve. 
By-pass  E  is  for  emerg- 
ency use  in  draining  off 
accumulated  water  and 
dirt,  should  the  valve 
clog.  With  such  an  ad- 
justment the  bonnet  of 
the  valve  may  be  re- 
moved for  inspection 
without  overflowing.  Be- 
fore the  steam  is  turned 
on  in  the  radiator  the  float  is  tipped,  as  shown  in  the  figure, 
making  a  small  wedge  shaped  opening  through  which  the 
vacuum  can  pull  on  the  radiator.  When  steam  is  admitted 
to  the  radiator,  condensation  flows  into  the  valve,  lifting 
the  float  and  sealing  the  outlet  against  the  passage  of 
steaim.  As  the  valve  continues  to  fill  with  water  the  float 

is  lifted,  and  water  passes 
to  the  vacuum  return.  As 
the  water  is  drawn  off  the 
float  falls  and  reseats  on 
the  nipple  when  about  % 
inch  of  water  remains  in 
the  valve,  thus  maintaining 
the  water  seal.  Fig.  82 
shows  the  piping  connec- 
tions around  'the  automatic 

pump  governor.     It  will  be 

Fig.   82.  seen    that    this    connection 


150  HEATING   AND    VENTILATION 

differs  from  those  of  the  Webster  and  VanAuken  Systems, 
in  that  the  pressure  in  the  return  main  controls  the  flow 
of  injection  water  into  the  suction  strainer. 

96.  Dunham  System: — The   special  valve  used  upon   the 
returns    from    radiators,    coils    and    drainage    points    in    the 
Dunham  System  is  shown  in  Fig.  83.     The  chamber  between 
the    two    corrugated  disks   AA   is   filled   with   a   liquid   which 
vaporizes   at  low  temperatures.     The  adjustment  is  so  made 
that  the  temperature  of  the  steam  creates  pressure  enough 
between   the   disks   to   close  the   valve   and   cut   off   drainage 

to  the  vacuum  pump.  When 
water  collects  under  the  disks 
the  temperature  of  the  water 
]RAD  is  sufficiently  cooled  below 
that  of  the  steam  to  condense 
some  of  the  liquid,  reduce  the 
pressure  and  open  up  the  valve. 
The  action  is  therefore  auto- 
matic and  controlled  entirely  by  the  temperature  of  the 
water  or  steam  in  contact  with  the  disks.  In  other  re- 
spects this  system  is  very  similar  to  those  previously  de- 
scribed. 

97.  Paul   System: — Referring   to  Art.    69  it  will  be  seen 
that  the  Paul  System  is  essentially  a  one-pipe  system,  with 
the  vacuum  principle  attached   to  the  air  valve.     Its   use   ia 
not  restricted   to  the  one-pipe  radiator,  since  it  may  be  ap- 
plied  to   the   two-pipe   radiator   as   well.      The   advantage    to 
be   gained,    however,    when   applied    to    the    former,    is    much 
greater  than  in  the  latter  because  of  the  greater  possibility 
of  air    clogging    the    one-pipe    radiator.      This    one    fact    has 
largely  determined   its  field   of  operation.     This  system  dif- 
fers  from  the   ones  just  mentioned   in  two   essential   points; 
first,   the  vacuum  effect  is  applied  at  the  air  valve  and  the 
water  of  condensation   is  not  moved  by  this  means;   second, 
the    vacuum    effect    is    produced    by    the    aspirator    principle 
using  water,  steam  or  compressed  air,  as  against  the  pumps 
used  by  the  other  companies.     The  same  principle  may  also 
be  applied  to   the   tank   receiving   the   condensation.   By   this 
means  it  is  possible  to  remove  all  the  air  in  the  system  and 
to    produce    a    partial    vacuum    if    necessary.    Ordinarily    the 
vacuum  is  supposed  to  extend   only  as  far  as  the  air  valve 
at  the  radiator.     If  desired,  however,  this  valve  may  be  ad- 


MECHANICAL   VACUUM  HEATING 


151 


justed  so  that  the  vacuum  effect  may  be  felt  within  the  radi- 
ator, and  in  some  cases  may  extend  into  the  supply  main. 
Many  modifications  of  the  Paul  System  are  being  used.  In  its 
latest  development,  the  layout  of  the  system  for  large  plants, 


I  AIR  VALVE 


VALVE 


OR  RETURN 


Fig.   84. 

Is  about  the  same  as  that  shown  in  Fig.  73,  where  all  of  the 
principal  pieces  of  apparatus  that  go  to  make  up  the  power 
room  equipment  are  present.  Fig.  84  shows  a  typical  vacu- 
um connection  between  one-pipe  and  two-pipe  radiators  and 
the  exhauster.  This  diagram  shows  the  discharge  leading 
to  a  tank,  sewer  or  catch  basin.  If  exhaust  steam  were 
used,  the  discharge  would  probably  lead  into  the  steam 
supply  to  one  or  more  of  the  radiators  and  then  into  the 
atmosphere.  Where  electric  current  can  be  had  this  ex- 
hausting  may  be  done  by  the  use  of  an  electric  motor.  A 
specially  designed  thermostatic  air  valve  is  supplied  by  the 
Company  to  be  used  on  this  system. 

Other  vacuum  systems,  each  having  a  full  line  of  specialty 
appliances,  might  be  mentioned  here  but  the  above  are  con- 
sidered sufficient. 


152  HEATING   AND    VENTILATION 

REFERENCES. 
References    on    Meehanieal    Vacuum    Heating:. 

TECHNICAL  BOOKS. 

Snow,  Principles  of  Heating,  Chap.  XL.  Carpenter,  Heating  £ 
"Ventilating  Buildings,  p.  285.  Hubbard,  Power,  Heating  &  Ventila- 
tion, p.  568. 

TECHNICAL  PERIODICALS. 

Engineering  Revieic.  Steam  Heating  Installation  in  the 
Biology  and  Geology  Building  and  the  Vivarium  Building, 
Princeton  University  (Webster  System),  Jan.  1910,  p.  27. 
Steam  Heating  and  Ventilating  Plant  Required  for  Addition 
to  Hotel  Astor  (Paul  System),  March  1910,  p.  27.  Heating 
Four  Store  Buildings  at  Salina,  Kans.,  (Moline  System,  Vacu- 
um Vapor),  April  1910,  p.  45.  Steam  Heating  System  for 
Henry  Doherty's  Mill,  Paterson,  N.  J.,  May  1910,  p.  37.  Heat- 
ing Residences  at  Fairfield,  Conn.,  (Bremen's  System  of 
Vapor  Heating),  June  1910,  p.  52.  Heating  Residence  at 
Flemington,  N.  J.,  (Vapor-Vacuum  System),  July  1910,  p.  43. 
Heating  System  Installed  in  the  Haynes  Office  Building, 
Boston,  (Webster  Modulation  System),  Aug.  1910,  p.  44. 
Heating  the  Silversmith's  Building,  New  York,  (Thermo- 
grade  System),  Jan.  1908,  p.  8.  Heating  System  in  the  New 
Factory  of'  Jenkins'  Bros.,  Ltd.,  Montreal,  Canada,  (Positive 
Differential  System),  Dec.  1907,  p.  14.  The  Railway  Review. 
Vacuum  Ventilation  for  Street  Cars,  Oct.  23,  1909,  p.  948. 
The  Metal  Worker.  A  Vapor  Vacuum  Heating  System,  April  4, 
1910,  p.  494.  Heating  Church  by  Vacuum  System,  Sept.  11. 
1909,  p.  46.  Rehabilitation  by  Vacuum  Heating,  Jan.  21,  1911. 
Power.  Combined  Vacuum  and  Gravity  Return  Heating  Sys- 
tem, Charles  A.  Fuller,  Aug.  11.  1911.  Vacuo  Hot  Water 
Heating,  Ira  N.  Evans,  Mar.  12,  1912.  Heat.  &  Vent.  Magazine. 
Vacuum  Heating  Practice,  J.  M.  Robb,  Jan.  1912. 


CHAPTER  X. 


MECHANICAL    WARM    AIR    HEATING    AND 
VENTILATION.      FAN    COIL    SYSTEMS. 


DESCRIPTION   OF  SYSTEMS   AND  APPARATUS  EMPLOYED. 

98.  Fire-places,  Stoves,  Furnaces  and  Direct  Radiation 
Systems    of    both    steam    and    hot    water    have,    individually, 
advantages    and    disadvantages,    but,    in    common,    all    lack 
what   is   increasingly  being   considered  as   of  more   import- 
ance   than    heating,    namely,    positive    ventilation.     Merely    to 
heat  a  poorly  ventilated  apartment  only  serves  to   increase 
the    discomfort    of    the    occupants,    and    modern    legislative 
bodies  are  reflecting  the  opinion  of  the  times  by  the  passage 
of    compulsory    ventilation    laws    affecting    buildings    with 
numerous    occupants,     such    as    factories,    barracks,    school 
houses,   hotels   and  auditoriums.     To   meet   this  demand   for 
the   positive   ventilation   of  such   classes   of  buildings,   there 
has  been  developed  what  is  variously  known  as  the  hot  Wast 
heating  system,  plenum  system,  fan  l)last  system    or  mechanical  warm 
air  system. 

99.  Elements    of   the    Mechanical    Warm    Air    System: — 

Known  by  whatever  name,  this  system  contemplates  the 
use  of  three  distinctly  vital  elements;  first,  some  form  of 
hot  metallic  surface  over  which  the  forced  air  may  pass 
and  be  heated;  second,  a  blower  or  fan  of  some  description 
to  propel  the  air;  and  third,  a  proper  arrangement  of  duct* 
or  passageways  to  distribute  this  heated  air  to  desired 
locations.  Figs.  96  and  97  show  these  essentials,  fan, 
heating  coils  and  ducts  in  their  relative  positions  with  con- 
nections as  found  in  a  typical  plant  of  this  system.  Many 
attachments  and  improved  mechanisms  may  be  had  to-day 
in  connection  with  this  system,  such  as  air  washers  and 
humidifiers,  automatic  damper  control  systems,  and  brine 
cooling  systems  whereby  the  heating  coils  may  be  used 
as  cooling  coils,  and,  during  hot  weather,  be  made  to 
maintain  the  temperature  within  the  building  from  10  de- 
grees to  15  degrees  lower  than  the  atmosphere.  None  of 
these  auxiliaries,  however,  change  in  any  way  the  necessity 


154 


HEATING    AND    VENTILATION 


for    the    three    fundamentals    named    and    their    general    ar- 
rangement as    shown. 

100.  Variations  in  the  Design  of  Mechanical  Warm  Air 
Systems: — With  regard  to  the  position  of  the  fan,  two  meth- 
ods of  installing  the  system  are  common.  The  first  and 
most  used  is  that  shown  in  Fig.  85,  a,  where  the  fan  is  in 
the  basement  of  the  building  and  forces  the  air  by  pressure 
upward  through  the  ducts  and  into  the  rooms.  This  causes 
the  air  within  the  entire  building  to  be  at  a  pressure 


b.      Exhaust  System. 


•a.     Plenum  System. 


slightly  higher  than  the  atmosphere,  and  hence  all  leak- 
ages will  be  outward  through  doors  and  window  crevices. 
A  system  so  installed  is  usually  called  a  plenum  system.  The 
fan  may,  however,  be  of  the  exhausting  type,  Fig.  85,  b, 
and  placed  in  the  attic  with  which  ducts  from  the  rooms 
connect,  so  that  the  fan  tends  to  keep  the  air  of  the  build- 
ing at  a  slight  vacuum  as  conrpared  with  the  atmosphere, 
thus  inducing  ventilation.  Air  is  then  supposed  to  enter 
the  basement  inlet,  pass  over  the  coil  surface,  and,  when 
heated,  pass  to  the  various  rooms  through  the  ducts  pro- 
vided. But  air  from  the  atmosphere  will  just  as  readily 
leak  in  at  windows  or  other  crevices,  as  come  in  over  the 


PLENUM    WARM    AIR    HEATING 


155 


heaters,  and  then  the  system  will  fail  in  its  heating  work. 
For  this  reason  the  exhaust  heatiny  system,  as  it  is  usually 
known,  is  seldom  installed,  except  where  aid  in  the  prompt 
removal  of  malodors  is  desired.  Combined  plenum  and  ex- 
haust systems  are  to  be  recommended  wherever  the  expense 
can  be  justified. 

101.  Blowers  and  Fans: — Many  methods  of  moving  air 
for  ventilating  and  heating  purposes  have  been  devised; 
some  positive  at  all  times,  others  so  dependent  upon  the  ex- 
istence of  certain  conditions  as  to  be  a  constant  source  of 
trouble.  It  is  coming  to  be  a  very  generally  accepted  fact, 
that  if  air  is  to  be  delivered  at  definite  times,  in  definite 
quantities  and  in  definite  places,  it  must  be  forced  there,  and 
not  merely  allowed  to  go  under  conditions  readily  changing 
or  disappearing.  The  recognition  of  this  fact  has  led  to  a 
very  common  use  of  the  mechanical  fan  or  blower  for  im- 
pelling air,  and  this  use  has,  in  turn,  caused  the  develop- 
ment of  fans  and  blowers  to  a  fairly  high  degree  of 
efficiency. 


Fig.   86. 

By  the  aid  of  mechanical  apparatus,  air  may  be  moved 
positively  in  either  of  two  ways,  by  the  exhaust  method  or 
by  the  plenum  method,  each  having  fans  developed  be.st  suited 
to  its  needs.  In  the  exhaust  method  the  fan  is  commonly 
of  the  disk  or  propeller  blade  type,  shown  in  Figs.  86  and 


156 


HEATING    AND    VENTILATION 


87,  ana  moves  the  air  by  suction.  It  is  usually  installed  In 
the  attic  or  near  the  top  of  the  building,  although  with  a 
system  of  return  ducts  it  may  be  installed  in  the  basement. 
The  plenum  system  uses  a  fan  of  the  paddle  wheel  or  mul- 
tiple blade  type,  shown  in  Figs.  88  and  89;  the  first  is  the 
standard  form  of  fan  wheel  in  common  use,  and  the  second 
is  a  more  recent  development  of  the  same,  called  the  "tur- 
bine" fan  wheel,  shown  direct  connected  to  a  De  Laval 
steam  turbine.  The  wheels  of  the  fans  are  also  shown. 


Fig.   87. 


Tests  of  the  latter  wheel  seem  to  show  a  somewhat  higher 
efficiency  than  has  heretofore  been  possible  with  the  older 
forms.  Both  of  these  forms  of  fans  are  used  in  plenum 
work,  and  are  placed  on  the  forcing  side  of  the  circulating 
system  just  between  the  air  intake  and  the  heater  coils, 
or  just  following  the  heater  coils,  and  hence  produce  a  pres- 
sure within  the  building  or  suite  heated,  so  that  leakages 
are  outward  and  not  so  detrimental  to  the  good  working 
of  the  plant  >as  in  the  exhaust  system. 

The  motive  power  for  fans  may  be  of  four  kinds, 
electric  direct  drive,  steam  engine  or  steam  turbine  direct 
drive,  and  belt  and  pulley  drive,  as  shown  in  Figs.  87,  88,  89 
and  90.  Which  of  these  drives  will  be  the  most  appropriate 
will  depend  entirely  upon  local  conditions  and  the  nature 


PLENUM    WARM    AIR    HEATING 


157 


of  the  available  power  supply.  The  steam  engine  or  steam 
turbine  drive  is  perhaps  the  most  common,  since  some 
steam  must  be  present  for  the  supply  of  the  heating  coils, 
and  since,  too,  the  exhaust  of  the  engine  or  turbine  may 
be  used  to  supplement  the  live  steam  used  for  heating. 
See  Art.  122. 


Fig.  89. 


Fan  housings  are  made  in  many  different  styles,  and 
of  various  materials,  the  more  readily  to  fit  any  given  set  of 
conditions.  Materials  employed  may  be  of  brick,  wood,  sheet 
steel  or  combinations  of  these.  Steel  housings  are  the  most 
common  and  are  made  in  such  a  variety  of  patterns  as 
will  fit  any  requirement  of  plenum  duct  direction.  What 
are  known  as  full  housings  are  those  in  which  the  entire  fan 
wheel  is  encased  with  steel  and  the  entire  unit  is  self-con- 
tained and  above  the  floor  line.  Three-quarter  housings  are 
those  in  which  only  the  upper  three-fourths  of  the  fan  wheel 
is  encased,  the  completion  of  the  air-sweep  around  the 


158 


HEATING    AND    VENTILATION 


paddles  being  obtained  by  properly  forming  the  brick  foun- 
dation upon  which  the  fan  is  installed.  The  larger  fans 
are  commonly  three-quarter  housed,  especially  if  they  are 
to  deliver  air  directly  into  underground  ducts.  Fig.  88 
shows  a  full  housing  and  Fig.  90  a  three-quarter  housing. 


Fig.    90.  Fig.   91. 

The  circular  opening  in  the  housing  around  the  shaft 
of  the  wheel  is  the  inlet  of  the  fan,  the  air  being  thrown 
by  centrifugal  force  to  the  periphery  and  at  the  same  time 
given  a  circular  motion,  thus  leaving  the  fan  tangentially 
through  the  discharge  opening.  Fans  may  be  obtained  which 
will  deliver  at  any  angle  around  the  circumference,  and  fans 
may  be  obtained  with  two  or  more  discharge  openings,  usu- 
ally referred  to  as  "multiple  discharge  fans,"  as  shown  in 
Fig.  91.  Some  fans  have  double  side  inlets,  i.  e.,  air  enters 
the  fan  from  each  side  at  the  center.  These  openings  are 
smaller  than  the  single  side  inlet.  All  fan  casements  should 
be  well  riveted  and  braced  with  angles  and  tee  irons.  The 
shaft  should  be  fitted  with  heavy  pattern,  adjustable,  self- 
oiling  bearings,  rigidly  fastened  to  the  casement  and  prop- 
erly braced.  The  thickness  of  the  steel  used  in  the  casement 
varies  according  to  the  size  of  the  fan,  from  No.  14  to  No.  11 
for  sizes  in  general  use.  The  fan  wheel  should  be  well  con- 
structed upon  a  heavy  spider  to  protect  against  distortion 
from  sudden  starting  and  stopping.  The  side  clearance  be- 
tween the  wheel  and  casement  should  be  small.  Fans  should 
be  bolted  to  substantial  foundations  of  brick  or  concrete. 
W.hen  connecting  them  to  metal  ducts  where  <any  sound  from 
the  motion  of  the  fan  may  be  transmitted  to  ithe  rooms,  the 
connection  should  be  made  through  flexible  rubber  cloth 


PLENUM    WARM    AIR    HEATING  159 

102.  Fresh  Air  Entrance   to    Building  and  to   Rooms: — 

The  air  may  enter  through  the  building  wall  at  the  ground 
level  or  it  may  be  taken  frdm  a  stack  built  for  the  pur- 
pose, providing  a  down  draft  with  entrance  for  the  air 
at  the  top.  This  may  be  done  in  case  no  washing  or  clean- 
ing systems  are  applied  and  in  case  the  air  is  heavily 
charged  with  dust  or  dirt  from  the  street.  Usually  in 
isolated  plants  or  in  small  cities,  the  air  is  taken  in  near 
the  ground  level  from  some  area-way  that  is  fairly  free 
from  dust.  In  the  larger  cities,  however,  either  a  washing 
system  is  installed  to  cleanse  the  air  before  it  is  sent 
around  to  the  rooms,  or  the  air  is  taken  from  an  elevation 
somewhat  above  the  ground  as  spoken  of  before.  The  ve- 
locity of  the  air  should  be  from  700  to  1000  feet  per  minute 
at  this  point  and  where  grill  work  or  shutters  of  any  sort 
are  put  in  the  opening,  they  are  usually  so  planned  as  not 
to  seriously  obstruct  the  flow  of  the  air.  Usually  a  plain 
flat  wire  screen  is  placed  in  the  opening  to  keep  out  leaves, 
and  doors  are  swung  from  the  inside  in  such  a  way  as  to  be 
thrown  open,  leaving  practically  the  full  value  of  the  open- 
ing as  a  net  area. 

Air  entrance  to  rooms  is  accomplished  through  registers 
or  gratings  which  cover  the  ends  of  rectangular  ducts  or 
conduits  called  stacks,  built  into  the  brick  walls  and  open- 
ing into  the  respective  rooms  much  as  shown  in  section  by 
Fig.  22.  Register  sizes  considered  standard  are  given  in 
Table  17,  Appendix.  The  velocity  of  the  air  at  a  plenum 
register  may  be  somewhat  higher  than  in  a  simple  fur- 
nace installation.  In  the  plenum  system  the  heat  reg- 
isters are  usually  placed  well  above  the  heads  of  the  occu- 
pants, near  the  ceiling,  and  the  vent  registers  near  the 
floor.  Velocities  allowable  at  registers  and  up  stacks  are 
shown  in  Table  XIII,  page  172. 

103.  Plenum    Heating    Surfaces: — 'Heating    surfaces    as 
used    to-day    in    connection    wit'h    plenum    systems    may    be 
divided   into   two   classes:   coil  surface,   made  of  loops  of   1    or 
1%    inch  wrought  iron  pipe  and  cast  surface,  made  of  hollow 
rectangular  castings  provided  with  numerous  staggered  pro- 
jections to  increase  the  outside  surface  and  provide  greater 
air    contact.    To    make    a    Jicatcr    of    either    kind    of    surface, 
successive  units  are  placed  side  by  side,   until  the  requisite 
total  area  and  depth  have  been  obtaiined.     The  total  number 
of  square   feet  of   cast   or  pipe   coil   surface   exposed   to    the 


160 


HEATING   AND    VENTILATION 


air  determines  the  total  number  of  heat  units  given  to  the 
air  per  hour,  wihile  the  depth  of  the  heater  controls  the  final 
temperature  of  the  air  leaving  the  heater.  Each  of  these 
points  must  be  considered  in  designing  the  heater  system. 
(See  Arts.  118  and  119). 

Pipe  coils  may  be  used 
under  high  pressures 
but  cast  coils  should 
never  be  used  under 
pressures  exceeding  25 
pounds  per  square  inch 
gage.  All  plenum  heat- 
ing surfaces  should  be 
well  vented  and  drained. 
Ample  allowance  also 
should  be  made  for  ex- 
pansion and  contraction. 
Coil  surface  is  of 
three  kinds,  that  hav- 
ing the  pipes  inserted 
vertically  into  a  hori- 
zontal  cast  iron  header 


92. 


wihich  forms  the  base  of  the  section,  Fig.  92,  that  having 
the  pipes  horizontally  between  two  vertical  side  headers, 
Fig.  93,  and  'that  having  one  header  vertical  and  one 
header  horizontal  called  the  mitre  coil,  Fig.  94.  The  first 
and  last  forms  shown  are  made  with  two,  three  or  four 

pipes  in  depth.  The  stand- 
ard number  of  pipes  in  any 
one  section  is  four.  Some- 
times these  pipes  are  spaced 
in  straight  lines  parallel 
with  the  wind  and  some- 
times are  staggered.  Stag- 
gered spacing  no  doubt 
makes  each  pipe  slightly 
more  efficient  but  it  adds 


Fig.   93. 
rent  and  power  to   the   fan. 


friction  to  the  air  cur- 
Efficiency  tests  of  both  spac- 
ings,  however,  show  little  difference  in  these  methods.  The 
horizontal  sections  and  the  mitre  sections  present  this  ad- 
vantage over  the  vertical  pipe  sections,  that  the  steam  and 
condensation  are  always  flowing  in  the  same  direction  and 


PLENUM    WARM   AIR    HEATING 


161 


? 


«§^ 

I3fe£ 


Condensation' 
Fig-.  95. 


drainage  is  very  simple.  With 
the  vertical  pipe  section, 
steam  in  one-half  of  the 
pipes  must  pass  upward 
against  the  direction  of  the 
flow  of  condensation  or  it  must 
carry  the  condensation  with  it. 
That  half  of  the  header  sup- 
plying pipes  which  carry 
steam  upward  is  usually 
drained  for  condensation  by 
a  small  hole  directly  into  the 
return  with  the  result  that 
steam  often  blows  through 
the  header  without  travers- 
ing the  pipe  circuits.  The 
third,  or  mitre  section,  in  ad- 
dition to  perfect  drainage,  haa 
perfect  expansion.  The  ver- 
tical header  serves  as  a 
steam  supply  and  the  horizon- 
tal header  as  a  drain,  permit- 
ting every  pipe  to  assume  any 
position  necessary  to  account 
for  a  reasonable  change  of 
length. 

Cast  iron  radiating  surface 
for  plenum  systems  is  .shown 
in  Fig.  95.  It  is  composed, 
primarily,  of  sections  not  un- 
like the  sections  of  an  ordi- 
nary direct  radiator  in  the 
way  in  which  they  are  joined 
together  at  the  top  and  bot- 
tom by  nipples,  thus  forming 
what  is  termed  a  stack.  Stacks 
are  again  assembled,  one  in 
front  of  another,  with  respect 
to  the  direction  in  which  the 
air  passes  through  them,  the 
completed  heater  being  then 
more  or  less  cubical  in  pro- 
portion. The  figure  shows  a 
heater  two  sections  in  depth 


162  HEATING    AND    VENTILATION 

and  ten  sections  in  width.  Provided  the  conditions  demand 
It,  the  heater  may  be  built  two  or  even  three  stacks  in 
height,  thus  doubling-  or  tripling  the  gross  wind  area.  See 
Art.  119. 

.  /Cast  iron  heaters  are  usually  of  the  Vcnto  type  and  are 
made  in  two  thicknesses,  6.75  and  9.125  inches  in  the  direc- 
tion of  the  air  velocity.  They  are  also  made  in  three 
heights,  40,  50  and  60  inches.  These  heaters  present  the  fol- 
lowing amounts  of  heating  surface:  6.75  inch  sections — 
7.5,  9.5  and  11  square  feet;  9.125  inch  sections — 10.75,  13.5 
and  16  square  feet  of  surface  for  the  40,  50  and  60  inch 
sections  respectively.  These  sections  give  such  a  variety  of 
sizes  as  to  permit  combinations  to  fit  almost  any  possible 
requirement  in  net  area,  gross  area  and  heating  surface. 
It  is  unusual  to  assemble  less  than  five  or  more  than  twenty- 
five  sections  to  the  stack.  By  the  proper  adjustment  of 
number  of  sections  to  the  stack,  and  of  stacks  to  the  heater, 
any  requirement  of  hot  blast  work  may  be  met. 

No  matter  what  kind  or  type  of  'heaters  may  be  selected, 
certain  methods  of  installing  them  have  become  common. 
They  may  be  placed  on  either  the  suction  or  the  force  side 
of  the  fan,  usually  the  former  in  drying  or  evaporating 
plants,  but  more  often  the  latter  in  heating  plants.  Because 
of  their  weight,  ample  and  firm  foundations  must  be  pro- 
vided. In  most  installations  for  heating  purposes,  w'here 
both  tempered  and  heated  air  is  supplied,  the  heater  should 
be  raised  on  its  foundation  18  to  24  inches  to  allow  a 
damper  and  passage  way  for  tempered  air. 

104.  Division  of  Coil  Surface: — It  is  considered  best 
practice  to  install  a  hot  -blast  heater  in  two  parts,  known 
as  the  tempering  coil  and  the  heating  coil.  In  the  calculations, 
Arts.  115-119,  the  total  heating  surfaoe  is  first  obtained  and 
then  this  is  split  up  into  whatever  arrangement  is  desired. 
The  tempering  coils  .should  be  placed  in  the  air  passage 
just  within  the  intake  for  the  building  and  should  contain 
from  one-fourth  to  one-third  of  the  total  heating  surface. 
In  this  way  the  air  is  tempered  before  it  reaches  any  other 
apparatus,  thus  protecting  from  accumulation  of  frost  on 
fan  and  bearings  and  aiding  in  the  process  o-f  lubrication. 
The  main  heat  coil  is  placed  just  beyond  the  fan  on  its  force 
side.  Referring  to  Figs.  96  and  97  it  will  be  seen  that  the 


PLENUM    WiARM    AIR    HEATING 


163 


PLAN. 


ELEVATION. 


Fig1.  96.  Fan  Room  Layout  with  Single  Ducts  along 
Basement  Ceiling  and  all  Mixing  Dampers  at  Plenum 
Chamber. 


HEATING    AND    VENTILATION 


Fig.   97.      Fan   Room   Layout   with   Double  Underground 
Ducts  and  Mixing-  Dampers  at  Base   of  Room  Stacks. 


.PLENUM    WARM   AIR    HEATING  165 

heating  coils  can  be  of  service  only  at  such  times  as  the 
fan  is  in  operation.  If  now  these  coils  were  split  up  into 
small  heaters  and  placed  at  the  foot  of  the  stacks  leading 
to  the  various  rooms  then  air  could  be  by-passed  through 
the  plenum  chamber  and  ducts,  over  the  various  radiating 
surfaces  to  the  rooms.  In  this  way  the  heaters  could  be 
used  as  indirect  gravity  heaters.  The  radiation  in  such  a 
case  would  be  insufficient  to  keep  the  rooms  at  the  same 
temperatures  as  if  the  same  amount  of  surface  were  placed 
in  the  plenum  coil  next  the  fan.  When  the  fan  is  in  oper- 
tion  the  air  is  moving  at  a  high  velocity  over  the  heating 
surface  and  the  rate  of  transmission  is  very  high.  On  the 
other  hand,  when  they  are  placed  at  the  foot  of  the  stacks 
and  used  as  indirect  heaters,  without  the  operation  of  the 
fan,  the  air  velocity  and  the  amount  of  heat  delivered  to 
the  rooms  are  correspondingly  reduced.  In  some  cases  the 
heating  coils  are  arranged  in  this  way  and  used  when  the 
building  is  not  occupied.  The  convenience  of  such  an  in- 
stallation can  readily  be  seen;  however,  the  expense  of  in. 
stalling  is  greater  than  where  they  are  assembled  as  coiis 
at  the  fan.  Exhaust  steam  from  the  engine  is  commonly 
used  in  the  tempering  coil  and  live  steam  of  low  pressure 
in  the  main  heating  coil.  This  may  be  varied  by  conditions, 
however,  and  all  surface  supplied  by  exhaust  steam  if  it  is 
thought  advisable. 

105.  Single  Duct  Plenum  System: — Duct  systems  in  hot 
blast  work  may  be  either  of  the  single  duct  type  or  the 
double  duct  type.  In  the  single  duct  plant,  every  horizontal 
duct  is  carried  independently  from  the  base  of  the  room  to 
be  heated  to  the  small  room  called  the  plenum  chamber,  which 
receives  the  hot  blast  from  the  heater.  This  chamber  is 
divided  into  an  upper  and  a  lower  part,  the  upper  receiving 
the  heated  air  that  has  been  forced  through  the.  heater, 
while  the  lower  part  receives  only  air  that  has  been  through 
the  tempering  coils,,  or  vice  versa.  The  leader  duct  from' 
the  base  of  each  vertical  room  duct  is  led  directly  opposite 
the  partition  between  these  two  chambers,  and  a  damper, 
regulated  by  some  system  of  ^automatic  control  from  the 
rooms  to  be  heated,  governs  whether  cool  air  from  the  lower 
chamber,  or  hot  air  from  the  upper  chamber,  or  a  mixture 
of  both,  shall  be  sent  to  the  rooms.  This  system  produces 
rather  a  complicated  net  work  of  dampers  and  ducts  at  the 
plenum  chamber  and  this  disadvantage  has  limited  its  use 
very  much. 


166 


HEATING   AND    VENTILATION 


106.  Double  Duct  Plenum  System: — As  its  name  indi- 
cates, this  system  runs  a  double  leader  duct  from  the 
plenum  chamber  to  the  base  of  each  vertical  room  duct,  the 
upper  one  of  these  ducts  being  in  direct  communication 
with  the  upper  part  of  the  plenum  chamber  and  carries 

hot  air,  while  the  lower 
one  is  in  communication 
with  the  lower  part  of 
the  plenum  chamber  and 
carries  cool  air.  No  mix- 
ing- or  throttling  is  done 
except  at  the  base  of  the 
vertical  room  duct,  where 
the  mixing  damper  is  lo- 
cated, it  being  controlled 
by  hand  or  automatically 
directly  from  the  room 
above.  With  this  scheme 
it  is  evident  that  the 
leader  ducts  for  each 
iroom  need  not  be  run 
singly,  but  all  the  ducts 
having  the  same  general 
direction  combined  in 
one  large  double  trunk, 
from  which  branches  are 
taken  to  the  various 
room  ducts  as  required. 
The  difference  between 

the   two    systems    is   shown   by    the    two    sketches,    Figs.    96 
and  97. 

A  hot  blast  plant  may  be  installed  as  a  basement  or  as 
a  sub-basement  system.  If  the  former,  the  leaders  will  be 
suspended  from  the  basement  ceiling  and  usually  con- 
structed of  sheet  metal,  thus  forming  what  is  often  called  a 
"false  ceiling."  If  the  latter,  they  will  be  just  below  the 
floor  of  the  basement  and  will  be  constructed  of  brick  and 
mortar,  or  of  concrete,  about  four  inches  thick.  For  designs 
of  conduits,  ducts  and  dampers,  see  Figs.  90,  96,  97  and 
98,  the  last  showing  a  simple  and  direct  installation  often 
applied  to  factories  of  several  stories.  Fig.  99  shows  a 
complete  steel  housed  plenum  unit  of  fan,  coils,  dampers 
and  duct  connections. 


Fig.  98. 


PLENUM    WARM    AIR    HEATING 


167 


Fig.   99. 


107.  Air  Washing;  and  Humidifying  Systems: — In  con- 
nection with  mechanical  warm  air  heating  and  ventilating 
systems,  there  is  often  installed  apparatus  for  washing 
and  humidifying  the  air.  In  crowded  city  districts  where 
the  air  is  laden  with  dust,  soot,  the  products  of  combus- 
tion and  other  harmful  gases,  its  purification  and  moisten- 
ing becomes  a  most  important  problem.  The  plenum  system 
of  heating  and  ventilating  lends  itself  most  readily  to 
the  solution  of  this  problem,  with  the  result  that  modern 
practice  is  tending  more  each  day  toward  the  combined 
installation  of  ventilating  and  humidifying  apparatus.  Fig. 
100  shows  a  plenum  system  augmented  by  an  air  washing, 
purifying  and  humidifying  apparatus. 

A  purifier  contemplates  the  installation  of  two  parts,  a 
washer  and  an  eliminator.  The  washer  is  built  in  the  main 
air  duct,  located  immediately  behind  the  tempering  coils, 
and  provided  with  streams  or  sprays  of  water  through 
Which  the  air  must  pass.  Numerous  schemes  for  breaking 
up  the  water  in  the  finest  sprays  are  on  the  market,  and 
their  relative  merits  may  be  judged  from  trade  literature. 
Having  caught  the  dust  particles  and  dissolved  the  soluble 
gases  from  the  air,  the  water  falls  to  a  collecting  pan  at 
the  bottom  of  the  spray  chamber,  and  from  there  is  again 
pumped  through  the  spraying  nozzles.  As  the  water  be- 
comes too  dirty  or  too  warm,  a  fresh  supply  is  delivered  to 
the  collecting  pan.  A  small  independent  centrifugal  pump 
is  commonly  used  for  the  circulation  of  the  spray  water. 

After  passing  through  the  washer,  the  air  next  encoun- 
ters the  eliminator,  the  purpose  of  which  is  to  remove  the 
surplus  moisture  and  water  particles  remaining  suspended 
in  the  air.  This  is  accomplished  by  an  arrangement  of 


168 


HEATING    AND    VENTILATION 


more  or  less  complicated  baffle  plates,  which  cause  the  air 
to  change  its  direction  suddenly  many  times  in  succession, 
with  the  effect  that  the  water  particles  impinge  upon  and 
adhere  to,  the  baffle  plates.  These  are  suitably  drained  to 
the  collecting-  pan  beneath  the  washer.  As  the  air  leaves 
the  eliminator  and  enters  the  fan  it  may,  with  good  ap- 
paratus, be  relieved  of  98  per  cent,  of  all  dust  and  dirt,  may 


Fig.  100. 


be  supplied  with  moisture  to  very  near  the  saturation  point, 
and,  in  summer  time  under  favorable  conditions,  may  be 
cooled  from  5  to  10  degrees  lower  than  the  atmosphere. 
This  is  due  to  the  cooling  effect  of  vaporizing  part  of  the 
water. 

Special  air  cooling  plants  have  been  installed  in  connec- 
tion with  the  plenum  system  of  ventilation,  whereby  refrig- 
erated brine  could  be  circulated  in  the  regular  heating  coils. 
The  description  of  such  a  plant  with  data,  may  be  found  in 
the  transactions  of  the  A.  S.  H.  &  V.  E.  for  the  year  1908. 


CHAPTER  XI. 


MECHANICAL,   WARM  AIR  HEATING  AND 
VENTILATION.     FAN  COIL,  SYSTEMS. 


AIR,    HEATING    SURFACE    AND    STEAM    REQUIREMENT. 
PRINCIPLES  OF  THE  DESIGN. 

108.  Definitions  of  Terms: — In  the  work  under  this  gen- 
eral heading1,  some  of  the  technical  abbreviations  that  are 
frequently  used  are  the  following:  H  =  B.  t.  u.  heat  loss 
per  hour  by  the  formula,  Hv  =  B.  t.  u.  heat  loss  per  hour  by 
ventilation,  H'  =  total  B.  t.  u.  loss  including  ventilation 
loss,  Q  =  cubic  feet  of  air  used  per  hour  as  a  heat  carrier, 
Qf  =  cubic  feet  of  air  used  including  extra  air  for  ventila- 
tion, R  —  total  square  feet  of  heating  surface  in  indirect 
heaters,  ta  —  temperature  of  the  steam  or  water  in  the 
heaters,  t  =  highest  temperature  of  the  air  at  the  register 
(let  this  be  the  same  as  the  temperature  of  the  air  upon 
leaving  the  heater),  tr  =  temperature  of  the  air  in  the  room, 
tv  =  temperature  of  the  air  at  the  register  when  extra  air 
is  used  for  ventilation,  to  =  temperature  of  the  outside  air, 
K  =  rate  of  transmission  of  heat  per  square  foot  of  surface 
per  degree  difference  per  hour,  N  =  the  number  of  persons 
to  be  provided  with  ventilation,  V  =  velocity  in  feet  per 
minute  and  v  =  velocity  in  feet  per  second.  Other  abbre- 
viations are  explained  in  the  text. 

100.  Theoretical  Considerations: — For  illustrative  pur- 
poses, references  will  frequently  be  made  throughout  this 
discussion  to  a  sample  plenum  design,  Figs.  104,  105  and  106. 
These  show  the  essential  points  of  most  plenum  work  an»I 
will  serve  as  a  basis  for  the  applications.  In  working  up 
any  complete  design  the  following  points  should  be  theo- 
retically considered  for  each  room:  the  heat  loss,  the  cubic 
feet  of  air  per  hour  needed  as  a  heat  carrier  (this  should 
be  checked  for  ventilation),  the  net  area  of  the  register 
in  square  inches,  the  catalog  size  of  the  register,  and  the 
area  and  size  of  the  ducts.  In  addition  to  these  the  follow- 
ing should  be  investigated  for  the  entire  plant:  the  size 
of  the  main  leader  at  the  plenum  chamber,  the  size  of  the 


170  HEATING   AND    VENTILATION 

principal  leader  branches,  the  square  feet  of  heating  sur- 
face in  the  coils,  the  lineal  feet  of  coils,  the  arrangements 
of  the  coils  in  groups  and  sections,  the  horse-power  and 
the  revolutions  per  minute  of  the  fan  including-  the  sizes 
of  the  inlet  and  the  outlet  of  the  fan,  the  horse-power  of 
the  engine  including  the  diameter  and  the  length  of  stroke, 
and  the  pounds  of  steam  condensed  per  hour  in  the  coils. 

Fresh  air  is  taken  into  the  building  at  the  assumed 
lowest  temperature,  to  degrees,  is  carried  over  heated  coils 
and  raised  to  t  degrees,  is  propelled  by  fans  through  ducts 
to  the  rooms  and  then  exhausted  through  vent  ducts  to  the 
outside  air,  thus  completing  the  cycle.  It  will  be  the  object 
to  so  discuss  this  cycle  that  it  will  be  general  and  so  it  will 
apply  to  any  case  which  may  be  brought  up. 

110.  Heat  Loss  and  Cubic  Feet  of  Air  Exhausted  per 
Hour: — It  is  assumed  here,  that  in  all  mechanical  draft 
heating  and  ventilating  systems,  the  circulating  air  is  all  taken 
from  the  outside  and  thrown  away  after  being  used.  Some  installa- 
tions have  arrangements  for  returning  the  room  air  to  the 
coils  for  reheating,  but  such  schemes  should  be  considered 
as  features  added  to  the  regular  design  rather  than  as  being 
a  necessary  part  of  it.  It  is  best  to  design  the  plant  with 
the  understanding  that  all  the  air  is  to  be  thrown  away, 
it  will  then  be  large  enough  for  any  service  that  it  is  ex- 
pected to  handle.  Having  found  H  by  some  acceptable 
formula,  the  total  heat  loss  is  (compare  with  Arts.  29  and 
36.) 

(Q   or  Q')    O'  —  to) 

H'  =  H  + (37) 

55 
When  t'  =  70  and  to  =  zero,  this  formula  reduces  ta 

H'  =  H  +  1.27  (Q  or  Q') 

To  determine  whether  Q  or  Q'  will  be  used  find  how  many 
people  would  be  provided  with  ventilating  air  with  the 
volume  Q.  If  Q  =  55  H  -r-  (t  —  f),  t  =  140  and  t'  =  70,  then 

55  H  H  H 

N  =  = =  approximately  (38) 

1800    (t — t')  2290  2300 

If  more  people  than  N  will  be  using  the  room  at  any  one 
time,  then  Q'  will  be  used  instead  and  this  value  would  be 
1800  times  the  number  of  persons  in  the  room.  In  any  or- 
dinary case,  Q  will  be  sufficient.  When  this  is  so,  formula 
37  reduces  to 

H'  =  2  H  (39) 


PLENUM    WARM    AIR    HEATING  171 

The  reasoning1  of  this  formula  is  easily  seen  when  it  is  re- 
membered  thdt  the  heat  given  off  from  the  air  in  dropping 
from  the  register  temperature,  140°,  to  the  room  tempera- 
ture, 70°,  goes  to  the  radiation  and  leakage  losses,  H,  while 
that  given  off  from  the  inside  temperature,  70°,  to  that  of 
the  outside  temperature,  0°,  is  charged  up  to  ventilation 
losses,  Hv.  Since  these  values  are  equal,  ti.'  =  H  +  Sv  =  2  H. 
APPLICATION. — Referring-  to  Fig.  105,  room  15,  and  Table 
XVI,  page  176,  it  is  seen  'that  the  calculated  'heart:  loss  H,  for 
this  room,  with  V  —  70  and  to  —  0,  is  70224  B.  t.  u.  per  hour; 
also,  that  the  cubic  feet  of  air,  Q,  if  t  =  140,  is  54775  per 
hour.  Applying  formula  39,  the  total  heat  loss,  H',  be- 
comes 140448  B.  t.  u.  per  hour,  or  twice  the  amount  found 
by  the  heat  loss  formula.  With  54775  cu'bic  feet  of  air  sent 
to  the  room  per  hour,  this  will  provide  good  ventilation  for 
thirty  persons.  Suppose,  however,  that  fifty  persons  were 
to  be  provided  for;  this  would  require  50  X  1800  =  90000 
cubic  feet  of  air  per  hour.  With  this  increased  number  of 
people  in  the  room,  the  total  heat  loss  would  not  be  as 
stated  above,  but  would  TDC  according-  to  formula  37. 

90000   (70  —  0) 

H'  =   70224   H =   184864. 

55 

111.     Temperature  of  the  Entering  Air  at  the  Register  t 

— In  plenum  work,  the  registers  are  placed  higher  in  the 
wall  and  the  velocity  of  the  -air  is  carried  a  little  higher 
than  in  furnace  work.  It  may  be  said  that  140°  is  probably 
the  accepted  temperature  for  design,  excepting  where  an 
extra  amount  of  air  is  demanded  for  ventilation  purposes. 
In  the  latter  case,  the  temperature  of  the  air  would  neces- 
sarily drop  below  140°  in  order  that  the  room  would  not  be 
overheated.  The  general  formula  is 

55  H 

tv  =  t'  +  (40) 

Q' 

APPLICATION. — Referring  to  room  15  and  (compare  -with 
Art.  38)  assuming1  the  heat  loss  to  have  been  figured  as 
before  with  ventilating  air  supplied  sufficient  for  50  per- 
sons, 90000  cubic  feet  per  hour,  then  the  temperature  of  the 
air  at  the  register  is 

55  // 

t  =  70  -i =  113° 

90COO 


172 


HEATING    AND    VENTILATION 


The  temperature  of  the  air  at  the  register  is  the 
same  or  slightly  less  than  the  temperature  of  the  air  upon 
leaving  the  coils.  If  this  room  were  to  be  the  only  one 
heated,  then  the  coils  would  be  figured  for  a  final  temper- 
ature of  the  air  at  113°,  but  other  rooms  may  have  air 
entering  at  higher  temperatures,  hence  the  temperature  t 
upon  leaving  the  coils  should  be  that  of  the  highest  t  at 
the  registers. 

112.  Cubic  Feet  of  Air  Needed  per  Hour: — The  following 
amount   of   air   will   be    needed   per   hour   as   a   heat   carrier 
(compare  with  Art.  36). 

55  H  H 

Q  = ;  where  t  =  140  and  t'  =  70,  Q  = 

t  —  t'  1.27 

If  extra  air  be   needed  for  ventilation,  Q'  =  1800  N. 

113.  Air    Velocities,    Y,    in    the    Plenum    System: — Table 
XIII  gives  the  velocities  in  feet  per  minute  that  have  been 
found   to  give  good  satisfaction   in   connection  with   blower 
systems. 

TABLE  XIII. 
Air  Velocities  in  the  Plenum  System. 


Fresh 
aii- 
intake 

Over 
coils 

Main 
duct 
near 
fan 

Smaller 
branch 
ducts 

Stacks 

Reg'rs 
or  other 
open'gs 

Offices, 
schools,  etc. 

|l 

800  to  1200  F.  P.  M. 
Average  1000  F.  P.  M. 

1200   to 
1800 
say  1500 

800  to 
1200 
say  900 

500  to 
700 
say  600 

300  to 
400 
say  300 

Auditoriums, 
churches,  etc. 

1500  to 
2000 
say  1800 

1000  to 
1500 
say  1200 

600  to 
800 
say  700 

400  to 
600 
say  400 

Shops  and 
factories. 

1500  to 
8000 
say  2000 

1000  to 
2000 
say  1500 

600  to 
1000 
say  800 

400  to 
800 
say  500 

114.      Cross    Sectional    Area    of   Registers,    Ducts,    etc.:— 

With  the  above  velocities  in  feet  per  minute,  the  square 
inches  of  net  opening  at  any  part  of  the  circulating  sys- 
tem can  be  obtained  by  direct  substitution  in  the  general 
formula 

144  (0  or  g') 


A  =  (Q  or  Q')  X  =  2.4 

60  V 


(41) 


PLENUM    WARM    AIR    HEATING  173 

The  calculated  duct  sizes,  of  course,  refer  to  the  warm 
air  duct.  The  cold  air  duct  in  double  duct  systems  need  not 
be  so  large  because  on  warm  days,  when  only  tempered  air 
is  needed,  the  steam  may  be  turned  off  from  one  or  more 
of  the  heaters  and  the  warm  air  duct  can  then  be  used  to 
furnish  what  otherwise  would  be  required  from  the  cold 
air  duct.  On  account  of  this  flexibility,  it  seems  only  nec- 
essary to  make  the  cold  air  duct  about  one-half  the  cross 
sectional  area  of  the  warm  air  duct.  For  convenience  of 
installation,  therefore,  it  would  be  well  to  make  the  former 
of  equal  width  to  the  latter  and  one-half  as  deep,  unless  by 
so  doing-  the  Cold  air  duct  becomes  too  shallow. 

APPLICATION.  —  Assuming  2000000  cubic  feet  of  air  to  pass 
through  the  main  heat  duct,  Fig.  104,  per  hour  at  the  veloc- 
ity of  1800  feet  per  minute,  the  duct  will  be  approximately 
20  square  feet  in  cross  section,  or  2%  by  8  feet.  The  two 
main  branches  at  B  will  carry  about  800000  cubic  feet  per 
hour  each  at  the  same  velocity  and  will  be  7.4  square  feet 
in  area  or,  say  2  by  4  feet.  The  same  branches  at  C  will 
carry  about  400000  cubic  feet  per  hour  each  at  a  velocity  of 
1500  feet  per  minute  and  will  be  4.4  square  feet  in  area  or, 
say  2  by  2V2  feet  and  the  branch  D  will  carry  about  300000 
cubic  feet  at  a  velocity  of  1200  feet  per  minute  and  will  be, 
say  1V2  by  2%  feet. 

The  stack  sizes  were  first  figured  for  the  velocity  of  600 
feet  per  minute.  These  sizes  were  then  made  to  fit  the  lay- 
ing of  the  brick  work  such  that  the  velocities  would  be 
anywhere  between  300  to  600  feet  per  minute.  The  net 
register  was  figured  for  an  air  velocity  of  300  feet  per 
minute  and  the  gross  registers  were  assumed  to  be  1.6 
times  the  net  area.  See  Art.  134. 

115.      Square  Feet  of   Heating  Surface,  R,  in  the  Colls:  — 

To  determine  theoretically  the  number  of  square  feet  of 
heating  surface  in  the  coils  of  an  indirect  heater,  the  fol- 
lowing formula  may  be  used: 


A"   (     /.  — 


(42) 


Rule. — To  find  the  square  feet  of  coil  surface  In  an  indirect 
heater,  divide  the  total  heat  loss  from  the  building  in  B.  t.  u.  per 
hour  by  the  rate  of  transmission,  multiplied  by  'the  difference  in 
temperature  between  the  inside  and  outside  of  the  coils. 


174  HEATING   AND    VENTILATION 

Since  the  coils  are  figured  from  the  entire  building  loss, 
Hf  will  include  the  sum  of  all  the  heat  losses  of  the  various 
rooms.  The  chief  concern  in  the  use  of  this  formula,  as 
stated,  is  to  determine  the  best  value  for  K,  the  rate  of 
transmission.  Prof.  Carpenter  in  H.  and  V.  B.,  Art.  62, 
quotes  extensively  from  experiments  with  coils  in  blower 
systems  of  heating  and  summarizes  all  in  the  formula,  K  = 
2+1.3  V~  where  v  =  average  velocity  of  air  over  the  coils 
in  feet  per  second.  With  the  four  velocities  most  appli- 
cable to  this  part  of  the  work,  i.  e.,  800,  1000,  1200  and  1500 
feet  per  minute,  this  becomes 

800  feet  per  minute  K  =  6.9 

1000  feet  per  minute  K  ==  7.3 

1200  feet  per  minute  K  =  7.8 

1500  feet  per  minute  K  =  8.5 

In  the  table  of  probable  efficiencies  of  indirect  radiators  in 
Art.  54  by  the  same  author,  the  values  are  somewhat  higher, 
being 

750  feet  per  minute  K  =    7.1 

1050  feet  per  minute  K  =    8.35 

1200  feet  per  minute  K  =    9. 

1500  feet  per  minute  K  =  10. 

The  values  of  K,  as  given  here,  are  certainly  very  safe 
when  compared  to  quotations  from  other  experimenters, 
some  of  them  exceeding  these  values  by  50  per  cent.  It 
is  always  well  to  remember  that  a  coil  that  has  been  in 
service  for  some  time  is  less  efficient  than  a  new  coil,  be- 
cause of  the  dirt  and  oil  deposits  upon  the  surface,  hence 
it  is  best  in  designing,  not  to  take  extreme  values  for  ef- 
ficiency. Assuming  K  =  8.5  and  1000  feet  per  minute  air 
velocity,  which  are  probably  the  best  values  to  use  in  the 
calculations,  also  ts  —  227  (5  pounds  gage  pressure),  t  = 
140  and  to  =  0,  formula  42  becomes 

E'  H'  E' 

R  — —  =  —    -say-  (43) 

1335  1400 


/                1'40  +  0\ 
S.5    (227 —  ) 


Table  XIV  quoted  by  Mr.  C.  L.  Hubbard  in  Power  Heat- 
Ing  &  Ventilation,  Part  III,  page  557,  gives  the  efficiencies 
of  forced-blast  pipe  heaters  and  the  temperatures  of  air 
delivered. 


PLENUM    WARM    AIR    HEATING 


175 


TABLE  XIV. 

Efficiencies  of  Forced-Blast  Pipe  Heaters,  and  Temperatures 

of    Air    Delivered. 
Velocity   of   air   over   coils   at    800    feet   per   minute. 


Rows 


Temp,  to  which  the  air         Efficiency  of  the  heating:  sur- 
will  be  raised  from  zero      i  face  in  B.t.u.  per  sq.ft.perhr. 


of  pipe 
deep 

Steam  pressure  in  heater 

Steam  pressure  in  heater 

51b. 

20  Ib. 

60  Ib. 

5  Ib. 

20  Ib. 

60  Ib. 

4 

30 

S5 

45 

1600 

1800 

2000 

6 

50 

55 

65 

1600 

1800 

2000 

8 

65 

70 

85 

1500 

1650 

1850 

10 

80 

90 

105 

1500 

1650 

1850 

12 

95 

105 

125 

1500 

1650 

1860 

14 

105 

120 

140 

1400 

1500 

1700 

16 

120 

130 

150 

1400 

1500 

1700 

18 

130 

140 

160 

1300 

1400 

1600 

20 

140 

150 

170 

1300 

1400 

1600 

For  a  velocity  of  1000  feet  per  minute  multiply  the 
temperatures  given  in  the  table  by  0.9  and  the  efficiencies 
by  1.1. 

Mr.  F.  R.  Still  of  the  American  Blower  Co.,  Detroit, 
gives  the  following  formula  for  the  total  B.  t.  u.  trans- 
mitted per  square  foot  of  surface  per  hour  between  the 
temperature  of  the  steam  and  that  of  the  entering  air. 

Total  B.  t.  u.  transmitted  =  c  VtT~(£*  —  to)  (44) 

In  which  case  v  is  the  velocity  in  feet  per  second  and  c  is 
a  constant  as  follows: 


176 


HEATING    AND    VENTILATION 


TABLE  XV. 
Values    of   c. 


Safe  factor 

Max.  factor 

1  section      4  rows  of  pipe 

3.45 

4.40 

2  sections    8  rows  of  pipe 

3-00 

3.40 

3  sections  12  rows  of  pipe 

2.63 

2.85 

4  sections  16  rows  of  pipe 

2.33 

2.45 

5  sections  20  rows  of  pipe 

2.12 

2  20 

6  sections  24  rows  of  pipe 

1.95 

2.05 

7  sections  28  rows  of  pipe 

1.80 

1.95 

8  sections  32  rows  of  pipe 

1.65 

1.85 

9  sections  36  rows  of  pipe 

1-52 

1-80 

10  sections  40  rows  of  pipe 

1.40 

1.75 

From  the  above  values  of  c,  Table  XVI  has  been   com- 
piled, assuming  ts  =  227,  to  =  0  and  c  =  a  safe  value. 

TABLE  XVI. 


Total  transmission  in  B.  t.  u.  per  sq.  ft.  per  hour. 
/*  =  227;  to  =  0. 


Velocity  < 
in  feet  pe 

Rows  of  pipe  deep. 

4 

8 

12 

16 

20 

24 

28 

32 

800 

2840 

2470 

2164 

1920 

1750 

1606 

1450 

1360 

1000 

3200 

2790 

2440 

2170 

1900 

1810 

1670 

1535 

1200 

8500 

8040 

2670 

2360 

2150 

1980 

1825 

1678 

1500 

8950 

8400 

2981 

2645 

2400 

2220 

2020 

1870 

Cast  iron  heaters  are  being  used  for  indirect  heating  in 
many  cases,  replacing  the  old-fashioned  pipe  coil  heaters. 
The  efficiency  of  these  heaters  is,  according  to  tests,  about 
the  same  as  that  of  the  pipe  coil  heaters  and  hence  formulas 
42  and  43  will  apply  to  both  pipe  and  cast  heaters.  Table 


PLENUM    WARM    AIR    HEATING 


177 


XVII  gives  values  of  heat  transmission  for  various  sections, 
taken  from  tests  upon  Vento  cast  iron  heaters  set  up  In 
banks,  and  is  added  as  a  means  of  comparison  with  the 
values  quoted  on  the  pipe  coil  heaters. 

TABLE  XVII. 

Rate    of    Transmission    of    Heat,    K,    through    Vento    Coils. 
Steam    227°,   Adr   Entering  at   0°. 

Velocities  of  air  over  coils. 


Sections 

800 

1000 

1200 

1500 

1 

7.6 

8.8 

10.0 

11.8 

2 

7.1 

8.2 

9.2 

10.5 

8 

6.6 

7-7 

86 

9-7 

4 

6.1 

7.1 

7.9 

9.0 

5 

6.6 

6.5 

7-8 

8.8 

6 

5.2 

6.0 

6.7 

7-7 

7 

4.8 

5-5 

6.2 

7-1 

In   applying  these   values   of  K  to   formula   42   it  should 

t  +  to 


be  remembered  that  to  would  be  used  instead  of 


2 


APPLICATION  1.  Where  Heating  Only  is  Considered. — Referring 
to  Table  XXV  let  H  for  the  entire  building  be  1483251. 
Then  from  Art.  112,  Q  =  1156935,  by  formula  39,  H'  =  2966502 
and  by  formula  43,  the  coil  surface  is 


R  — 


2966502 


.5^227  - 


=  2222  square  feet. 


140  +  0\ 

—T-  ) 

With   three    lineal   feet   of   1    inch    pipp    per   square    foot    of 
surface,  we  have  6666  lineal  feet  of  coils  in  the  heater. 

APPLICATION  2.     Where  Ventilation  is  Considered.  —  Assume  1100 
people  in  the  building  on  a  zero  day  and  Q'  =  2000000,  then, 
H'  =  148-3251  +  1.27  X  2000000  =  4023251  and 

4023251 

=3014  sq.  feet  =  9042  lineal  feet. 


R  = 


/ 

8.6  (227 


140 


178  HEATING  AND  VENTILATION 

This  value  is  probably  the  greatest  amount  that  would 
be  needed.  In  such  a  case,  when  the  rooms  are  supplied 
with  extra  air,  the  register  temperatures  over  the  entire 
building1  may  be  less  than  140  degrees.  Suppose  in  this 
case  the  temperature  is,  by  formula  40,  t  =  70  +  55  X  1483251 
-T-  2000000  ==•  111°,  then 

4023251 

=  2760  sq.  ft.  =  8280  lineal  ft. 


/ 

•5(227- 


111 


2 

In  using1  this  formula,  the  value  t  =  140  is  to  be  recom- 
mended wherever  part  of  the  rooms  are  not  provided  with 
extra  amounts  of  ventilating-  air.  By  so  doing-  the  ducts  and 
registers  may  be  held  down  to  a  more  moderate  size  and  at 
the  same  time  give  a  safer  figure  for  the  heating-  surface. 

Suppose  that  in  a  certain  building  most  of  the  rooms 
are  to  be  ventilated  and  that  these  rooms  will  have  large 
amounts  of  air  delivered  at  low  temperatures.  In  such  a 
case  it  will  be  economy  to  heat  the  air  for  all  rooms  to  this 
temperature  and  supply  more  air  to  the  rooms  that  would 
otherwise  be  heated  with  air  at  140  degrees,  -than  to  put 
in  a  heater  large  enough  to  heat  all  the  air  to  140  degrees 
and  then  dilute  with  large  amounts  of  cold  air  to  lower  the 
temperature  to  what  it  should  be.  Again,  suppose  that  a 
school  building-  contains,  in  addition  to  the  regular  class 
rooms,  laboratories,  etc.,  an  auditorium  and  gymnasium,  the 
two  together  requiring  an  amount  of  air  sufficient  to  justify 
a  separate  fan  system  (a  condition  which  frequently  exists), 
it  would  be  economy  to  separate  the  heating  system  for 
these  rooms  from  the  rest  of  the  building  because  of  the 
comparatively  short  time  the  rooms  are  in  use.  When  not 
in  use  the  fan  unit  may  be  shut  down  without  interfering 
with  the  rest  of  the  system.  On  the  other  hand,  if  united 
wi-th  the  rest  of  the  building,  the  capacity  of  the  unit  would 
be  reached  only  when  these  rooms  were  in  use,  while  at 
other  times  it  would  run  at  a  very  low  efficiency. 

116.  Approximate  Rules  for  Plenum  Heating  Surfaces: 
— The  following-  approximate  rules  are  sometimes  used  in 
checking-  up  heating-  surface  in  the  coils.  These  are  not 
recommended  and  should  be  used  with  caution. 

Rule  1. — "Allow  one  lineal  foot  of  \  inch  pipe  for  each  65  to 
125  cubic  feet  of  room  space";  65  for  office  buildings,  schools,  etc., 
and  125  for  shops  and  laboratories.  Since  this  building  has  approx- 
imately 500000  cubic  feet  of  room  space,  it  gives  7700  lineal  feet 
of  1  inch  pipe  in  the  heater. 


PLENUM    WARM    AIR    HEATING 


179 


Rule  2. — "Alloiv  200  lineal  feet  of  1  inch  pipe  for  each  1000 
cubic  feet  of  air  per  minute  at  a  velocity  of  1500  feet  per  minute." 
Applying  to  the  above  building  when  the  air  moves  over  the  coils  at 
1000  feet  per  minute,  the  heated  surface  is  only  about  four- fifths  as 
valuable  and  ivould  require  250  lineal  feet  per  each  1000  cubic  feet 
of  air  per  minute.  This  gives  8333  lineal  feet  of  coils. 

117.  Final  Air  Temperatures: — Since  the  amount  of 
heat  transmitted  is  directly  proportional  to  the  difference 
of  temperature  between  the  two  sides  of  the  metal,  the  first 
coils  in  the  bank  are  the  most  efficient,  and  this  efficiency 
drops  off  rapidly  as  the  air  becomes  heated  in  passing  over 
the  coils.  Final  temperatures  for  different  numbers  of  coil 
sections  in  banks  have  been  found  by  experiment  and  may 
be  taken  from  Table  XVIII.  See  also  Table  XIV,  page  175. 


TABLE  XVIII. 

Temperatures    of   Air   upon   Leaving   Coils,    Steam    227°,   Air 
Entering  at  0°. 


Sections 

No.    of 
Bows 

Velocities  of  air  through  coils  In  F.  P.  M. 

890 

1000 

1200 

1500 

1 

4 

42 

33 

28 

23 

2 

8 

71 

62 

56 

52 

3 

12 

96 

87 

80 

75 

4 

16 

119 

108 

101 

93 

5 

SO 

136 

125 

116 

108 

6 

24 

153 

140 

131 

120 

7 

28 

169 

155 

143 

131 

8 

82 

183 

166 

154 

141 

These  temperatures  may  be  increased  about  10  per  cent, 
for  20  pounds  gage  pressure. 

Table  XIX  shows  similar  results  quoted  for  the  Vento 
cast  iron  heaters. 


180 


HEATING    AND    VENTILATION 


TABLE  XIX. 

Temperatures  of  Air  upon  Leaving  Vento  Coils,  Steam  227 

Air   Entering  at    0°.      Regular   and  Narrow   Sections 

5   Inch  Centers. 


ft 

o-o 

j_,  oa 

pfi  w 

Velocities  of  air  through  coils  in  F.  P.  M. 

800 

1000 

1200 

1500 

0° 

-10° 

-20° 

0° 

-10° 

-20° 

0° 

-10° 

-20° 

0° 

-10° 

-20° 

1       Reg. 
Nar. 

88 

85 

82 

30 

2      JReg. 

(58 

61 

E5 

63 

55 

48 

59 

51 

44 

53 

45 

88 

|Nar. 

61 

48 

36 

46 

38 

31 

43 

35 

39 

31 

8      iReg. 

93 

87 

82 

87 

80 

75 

82 

75 

69 

74 

68 

61 

jNar 

70 

64 

57 

65 

58 

52 

61 

64 

47 

65 

48 

41 

4     iReg. 

113 

108 

103 

106 

100 

96 

100 

95 

80 

92 

86 

81 

INar. 

88 

82 

77 

82 

76 

70 

77 

70 

64 

70 

68 

66 

6 

Reg. 

130 

126 

122, 

122 

118 

114 

116 

111 

107 

108 

102 

97 

Nar. 

103 

97 

93 

96 

90 

86 

90 

84 

80 

83 

77 

71 

6 

Reg. 

143 

140 

136 

136 

132 

128 

129 

125 

121 

120 

116 

112 

Nar. 

115 

111 

107 

108 

104 

100 

102 

98 

93 

94 

89 

84 

7 

Reg. 

154 

151 

148 

147 

144 

141 

141 

137 

133 

132 

128 

124 

Nar. 

127 

123 

120 

120 

115 

111 

114 

109 

105 

105 

100 

96 

118.  Arrangement  of  Coils  In  Pipe  Heaters: — Coil  sec- 
tions are  arranged  with  2,  3  and  4  rows  of  pipes  per  sec- 
tion. Unless  special  reference  is  made  to  this  point,  the 
latter  value  is  understood.  Having  found  the  total  square 
feet  of  heating  surface  in  the  heater,  obtain  from  the  tern- 
perature  tables  the  number  of  sections  deep  the  heater  will 
need  to  be  to  produce  the  desired  temperature,  and  find  the 
number  of  square  feet  of  heating  surface  per  section  and 
per  row  of  coils.  Let  this  latter  value  be  A.  Also  find  the 
net  wind  area  across  the  coils,  assuming,  say  1000  feet  per 
minute  velocity.  From  the  net  wind  area,  find  the  gross 
cross  sectional  area  of  the  heater  by  the  value 

Gross  wind  area  =2.5  times  net  wind  area.  (45) 

From  the  gross  area  the  size  of  the  heater  may  be  selected. 
In  selecting  the  heater,  the  following  check  should  be  ap- 
plied. Find  the  number  of  square  feet  of  heating  surface, 
B,  in  each  row  of  the  coils  as  figured  from  the  gross  area 
and  compare  with  A.  These  must  be  made  to  agree. 

Let   the    net    area   between    the    tubes,    N.    A.,    the    space 


PLENUM    WARM    AIR    HEATING  181 

occupied  by  the  tubes,  T.  A.,  and  the  gross  cross  sectional 
wind  area  through  the  tube,  G.  W.  A.,  be  respectively 

Q  or  Q'  Q  or  Q'  Q  or  Q' 

N.  A.  — ;  T.  A.  — ;  and  O.  W.  A.  = (46) 

60   V  40  7  24   F 

Since  the  cross  sectional  space  T.  A.  occupied  by  the  tubes 
is  to  the  coil  surface  per  row  as  1  :  3.1416,  the  total  coil 
surface  in  one  row  of  tubes  is 

3.1416   (Q  or  Q') 


40   F  F 

Reduced  to  the  basis  of  the  net  area,  N.  A.,  we  have 

RI  =  4.8  times  N.  A.  (47) 

If  B  is  greater  than  A,  then  the  total  heating  surface 
must  be  increased  in  that  proportion,  since  the  number  of 
sections  cannot  be  less  or  the  final  temperature  will  drop 
below  the  required  degree,  and  the  net  cross  section  cannot 
be  less  or  the  velocity  of  the  air  will  be  greater  than  that 
desired.  On  the  other  hand,  suppose  B  should  be  less  than 
A.  In  that  case  the  total  heating  surface  will  not  change 
from  that  calculated.  Either  B  may  remain  the  same  as 
calculated  and  the  number  of  sections  increased  (if  de- 
sirable) until  all  the  heating  surface  is  accounted  for,  or  A 
may  remain  constant  and  B  may  be  increased.  The  latter 
method  is  probably  a  better  one  since  it  gives  larger  wind 
areas  and  consequently  reduced  velocities  of  the  air,  which 
in  many  cases  is  desirable,  and  avoids  placing  heating  .sur- 
face at  the  rear  of  the  bank  where  it  is  less  efficient. 

Assembled  sections  of  pipe  coil  heaters  are  supplied  by 
manufacturers  from  the  smallest  size  of  3  feet  x  3  feet,  to 
the  largest  size  of  10  feet  x  10  feet;  these  dimensions  being 
those  of  the  gross  cross-sectional  area,  and  not  dimensions 
overall.  Between  the  two  limits,  both  height  and  breadth 
usually  vary  by  6  inch  increments.  For  exact  sizes,  consult 
dimension  tables  in  manufacturers'  catalogs. 

APPLICATION  1.— In  Article  115,  let  R  =  2222,  Q  ='1156935, 
V  =  1000  and  t  =  140;  then  from  Table  XVIII  the  heater  will 
require  24  rows  of  coils  in  depth  to  give  the  required  tem- 
perature. Next  find  RI  =  93  square  feet  of  heating  surface 
per  row,  also 

N.  A.  —  19.7;  T.  A.  =  29.6;  and  G.  W.  A.  =  48.3. 
Checking  N.  A.   with   an   air  velocity   of    1000   feet  per  min- 
ute gives   1156935  -H   (60    X   1000)   =  19.3   square   feet,   which 


182  HEATING   AND    VENTILATION 

shows  that  the  above  arrangement  is  satisfactory.  Now 
from  the  value  G.  W.  A.  =  48.3  select  a  heater,  say  6  feet 
X  8  feet. 

APPLICATION  2. — In  article  115,  let  R  =  3014,  Q'  =  2000000, 
V  —  1000  and  t  =  140;  then  as  before,  the  heater  will  need 
24  rows  of  coils.  Find  in  this  case  RI  =  126  and 

N.  A.  =  26.3;  T.  A.  =  39.4;  and  G.  W.  A.  =  65.7. 
Checking  from  the  volume  of  air  delivered,   obtain 

N.  A.  =  33.3;   T.  A.  =  50;   and   G.  W.  A.  =  83.3. 
From  N.  A.  =  33.3   find  -Ri  =  160,  which  shows  that  it  will 

160 

be   necessary  to   increase  the  total   heating  surface  to 

126 

X  3014  =  3826  square  feet.  If  it  were  considered  advisable 
to  have  1200  feet  air  velocity  the  heating  surface  per  row 
would  be  reduced  to  135  and  the  temperature,  t,  would  be 
reduced  to  131.  Both  conditions  are  reasonable  and  in  many 
cases  would  be  considered  satisfactory. 

Selecting  the  heater  for  the  gross  area  of  83.3  square 
feet,  from  the  catalog  size,  would  probably  give  a  single 
section  9  feet  X  9  feet  or  a  double  section,  each  part  6 
feet  X  7  feet. 

110.  Arrangement  of  Sections  and  Stacks  in  Vento  Cast 
Iron  Heaters: — Applying  only  to  Case  2,  Art.  115,  let  R  = 
3014,  Q'  =  2000000,  V  =  1000,  N.  A.  (least  value)  =  33.3,  and  t 
=  140. 

From  Table  48,  Appendix,  either  of  the  following  ar- 
rangements will  give  the  necessary  N.  A.  First. — Six  stacks 
deep,  two  sections  high,  50  inches  on  top  of  60  inches  and 
twenty  sections  wide.  This  makes  a  total  of  590  square 
feet  to  the  stack  or  3540  square  feet  total.  The  gross  wind 
area  looking  in  the  direction  of  the  wind  is  103  inches  by 
110  inches.  Second. — Six  stacks  deep,  two  sections  high,  60 
inches  on  top  of  60  inches  and  eighteen  sections  wide.  This 
makes  a  total  of  576  square  feet  to  the  stack  or  3456  square 
feet  total.  The  gross  wind  area  looking  in  the  direction 
of  the  wind  is  93  inches  by  120  inches.  These  arrangements 
will  guarantee  a  temperature  of  136  degrees  upon  leaving 
the  coils.  If  this  temperature  is  not  sufficient  then  the 
coils  must  be  made  seven  sections  deep  and  the  total  heat- 
ing surface  arbitrarily  increased.  Other  arrangements 
could  be  worked  out  with  4%  inch  and  5%  inch  spacings. 
Also,  narrow  sections  could  be  used  in  place  of  the  regular. 
It  will  be  found,  however,  that  the  two  stated  are  probably 


PLENUM    WARM   AIR    HEATING  183 

the  best  arrangements  that  could  be  made.     (See  Table  XIX 
for   temperatures.) 

120.  Use  of  Hot  Water  in  Indirect  Coils: — In  most  cases 
low  pressure  steam  is  used  as  a  heating  medium  in  the  in- 
direct coils.     It  is   possible,   however,   to   use   hot  water   in- 
stead,  where   a  good  supply  is   to   be  had.     In   such  an  ar- 
rangement the  coils  will  be  figured  from  formula  42,  using 
all   values  the   same  as  for   steam   excepting   ts,   which   will 
fee  repilaced  by  the  average  temperature  of  the  water.     The 
piping   connections    and   the   arrangement    of  the   coils    will 
follow  the  same  general  suggestions  as  already  stated. 

121.  Pounds    of    Steam    Condensed   per    Square    Foot    oi 
Heating   Surface   per   Hour: — From   Art.    115   the   number  of 
pounds  of  condensation  per  hour  per  square  foot  of  surface 
in  the  coils  is 

H' 

m   =  — (48) 

R  X  Heat  given  off  per  pound  of  condensation. 

APPLICATION. — Let  R  =  3014  and  Hr  =  4023251;  also  let 
one  pound  of  dry  steam  at  five  pounds  gage  in  condensing 
to  water  at  212  degrees  give  off  1155.6  —  180.9  =  974.7.  (See 
Tables  4  and  8,  Appendix),  then 

4023251 

m  = —  =1.37  pounds. 

3014   X   974.7 

This  amount  should,  of  course,  be  considered  an  average. 

The  first  and  last  section  in  any  bank  would  vary  above 
and  below  this  amount  by  as  much  as  50  per  cent,  in  the 
average  plant.  The  first  coils  may  condense  as  much  as  2 
pounds  of  steam  per  square  foot  of  surface  per  hour. 

122.  Pounds    of    Dry    Steam    Needed    in    Excess    of    the 
Exhaust  Steam  Given  off  Prom  the  Engine: — Let   the  heat- 
ing   value    of    the    exhaust    steam    from    the    engine    be    85 
per   cent,    of   that    of   good   dry    steam,    also   let    the    engine 
use  40  pounds  of  dry  steam  per  horse  power  hour  in  driv- 
ing the  fan.     From  Art.  132,  the  engine  will  use  40   X   13.6 
=  544  pounds  of  steam  per  hour  and  the  heating  value  will 
be  974.7  X  .85  =  828  B.  t.  u.  per  pound  or  828  X  544  =  450432  B. 
t.   u.    total   per  hour.     Then   4023251  —  450432  =  3572819   B. 
t.    u.,    and    3572819    -r-   974.7    =   3664    pounds    of   steam.      The 
boiler  will  then  supply  to  the  engine  and  coils,   3664  +  544 
=  4208  pounds   of  steam  total   and  will   represent,  approx- 
imately,  4208  -r-  30  =  140  boiler  horse  power. 


CHAPTER  XII. 

MECHANICAL    WARM    AIR    HEATING    AND 
VENTILATION.      FAN    COIL    SYSTEMS. 


PRINCIPLES    OF    THE    DESIGN,    CONTINUED. 
FANS    AND    FAN    DRIVES. 

123.     Theoretical  Air  Velocity: — The   theoretical  velocity 
of  air  v,   flowing  from  any  pressure,  pa,   to  any  pressure,  pb, 


is  obtained  from  the  general  equation  v  =  }/2gh,  where  v 
is  given  in  feet  per  second,  g  =  32.16  and  Ji  =  head  in  feet 
producing  flow.  This  latter  value  may  be  easily  changed 
from  feet  of  head  to  pounds  pressure  and  vice  versa. 

When  exhausting  air  from  any  enclosed  space  into 
another  space  containing  air  at  a  different  density,  the 
force  which  causes  movement  of  the  air  is  pa  —  p&  =  px. 
These  recorded  pressures  may  be  taken  by  any  standard 
type  of  pressure  gage  and  show  pressures  above  the  at- 
mosphere. When  exhausting  into  the  atmosphere,  the  value 
Pb  is  zero  and  pa  =  px.  The  fact  that  a  difference  of  pres- 
sure exists  between  two  points  indicates  that  there  are 
either  two  actual  columns  (or  equivalent  as  in  Fig.  8)  of 
air  at  different  densities  connected  and  producing  motion, 
or  that,  by  mechanical  means,  a  pressure  difference  is  crea- 
ted which  may  easily  be  reduced  to  an  equivalent  head  h, 
in  feet,  by  dividing  the  pressure  head  by  the  density  of  the 
air,  as 

pressure  difference  pa  —  p& 


Ji  = 


density  d 

Let  pa  —  pb  =  px  =  ounces  of  pressure  per  square  inch  of 
area  producing  velocity  of  the  air;  also,  let  g  =  acceleration 
due  to  gravity  =  32.16  and  d  =  density,  or  weight,  of  one 
cubic  foot  of  dry  air  at  60  degrees  and  at  atmospheric  pres- 
sure (Table  12,  Appendix),  then,  substituting  'in  the  general 
equation,  we  have 


64.32   X   144p* 

=  87   Vf*  (49) 


.0764    X    16 

Since  the  pressure  producing  flow  is  usually  measured 
in  inches  of  water,  Jiw,  the  above  can  be  changed  to  equiva- 
lent height  of  air  column  by 

weight  of  water,  per  cu.  ft.  at  given  temp.   X  Tiw 


weight  of  air  at  given  temperature  X  12 


(50) 


PLENUM    WARM    AIR    HEATING  185 

Applying1   this   to   dry    air   at   60    degrees   and    water  .at  the 

same  temperature  (Tables  12  and  8,  Appendix,  also  Art.  15), 

62.37 


=  68  h 


12    X   .0764 
then  substituting  in  the  general  equation,  find 

v  =  V64T32  X  68  /TuT—  66.2  Vfc~  (51) 

Formula  50  at  the  temperatures  50,  55,  60,  65  and  70 
degrees  respectively,  gives  results  varying  between  v=  65.5 
V/^Tfor  50  degrees  and  v  =  66.5  Vft^'  for  70  degrees,  which 
leads  to  the  approximate  general  rule  that  the  theoretical 
velocity  of  air,  when  measured  by  a  water  column  gage  that  meas- 
ures in  incites  of  water,  equals  sixty-six  times  the  square  root  of  the 
height  of  the  column  in  inches.  Stated  as  a  formula 

v  =  66    \ffi"  (52) 

for  calculations  requiring  accuracy,  several  factors  af- 
fect the  final  result;  atmospheric  pressure,  humidity,  and 
the  density  and  change  of  temperature  in  the  air  current- 
Let  the  atmospheric  pressure  and  the  humidity  be 
constant,  since  these  would  affect  the  result  but  little,  and 
first  take  into  account  t^  "  density  of  the  air.  Let  the 
pressure  of  the  atmospher^  be  29.92  inches  of  mercury 
(14.7  pounds  =  235  ounces  per  square  inch  area)  then, 
since  the  density  is  proportional  to  the  absolute  pressure, 
the  temperature  remaining  constant,  we  have  from  form- 
ula 49  with  air  exhausting  into  the  atmosphere. 


V64.32    X    144  px                              I            p* 
=   1336  J (53) 
235   +  px                         \    235   +  px 

.0764  X  16  X 

235 

Also    from    the    relation    existing    between    formulas    49    and 
51,  formula  53  reduces  to 


Vhw 
(54) 
407  +  hv, 

From    formulas    53    and    54    the    second    columns    in    Tables 
XX  and  XXI  have  been  calculated. 

APPLICATION. — Air  is  exhausted  from  an  orifice  in  an  air 
duct  into  the  atmosphere.  The  pressure  of  the  air  within 
the  duct  is  one  ounce  by  pressure  gage  or  1.74  inches  by  a 
Pitot  tube.  Assuming  the  air  to  be  dry  and  the  barometer 
standing  at  29.92  inches  when  the  water  in  the  tube  is  60 
degrees,  what  is  the  velocity  of  the  air?  By  the  approxi- 
mate formulas  49  and  52 


186 


HEATING    AND    VENTILATION 


v  —  87  VI  =  87  F.  P.  8. 
and  v  —  66  V~1^4  =  87.2  F.  P.  8. 
By  formulas  53  and  54 


v  =  1336 


and  v  =  1336 


/     •      1 
>      235+1 


+ 
T7T4" 


86.3  F.  P.  8. 


407  +  1.74 


=  87.1  F.  P.  8. 


TABLE  XX. 
Column  2  figured  from  formula  53. 


Pressure  in  ounces 
per  sq.  incn. 

Velocity  of  dry  air  at  6QQ  es- 
cap.ng  into  the  atmosphere 
through  any  shaped  orifice  in 
any  pipe  or  reservoir  in  which 
a  given  pressure    is    main- 
tained. 

Vol.  of  air  in  cu. 
ft.  which  may  be 
discharged   in  1 
min.  through  an 
orifice  having  an 
effective  area  of 
discharge    o  f    1 
sq.  inch. 

Ool.  8  -f-  144 

H.  P.  required  to 
move    the  given 
vol.  of  air  under 
the   given    con- 
ditions    o  f    dis- 
charge. 

(Col.  3  X  Col.  1) 

Ft.  per  sec. 

Ft.  per  min. 

16  X  33000 

% 

30-80 

1848-00 

12.83 

0.00044 

% 

43  56 

2613.60 

18.15 

0.00124 

% 

53-27 

8196  20 

22.19 

0.00227 

% 

61.56 

8693-60 

25-65 

0.00349 

H 

68.79 

4127-40 

2866 

0.00489 

H 

75-35 

4521.00 

31.47 

0.00642 

7A 

81.87 

4882.20 

33.90 

0.00809 

1 

86.97 

5218-20 

36-24 

0.00988 

IK 

92.18 

5530-80 

38.41 

0.01178 

ik 

97  18 

5830.80 

40.49 

0.01380 

& 

101.90 

6114.00 

42.46 

0.01592 

llA 

106.40 

6384.00 

44.33 

0.01814 

l% 

110.82 

6649.20 

46.11 

0.02046 

IK 

114.86 

6891-60 

.47.86 

0.02284 

IK 

118.85 

7131  00 

49.52 

0.02533 

2 

122  47 

7348-20 

51.08 

0.02787 

PLENUM    WARM    AIR    HEATING 


187 


TABLE  XXI. 
Column   2   figured   from  formula  54. 


Pressure 
head  in 

Velocity  of  dry  air  at  6QQ  escaping:  into  the  atmosphere 
through  any  shaped  orifice  in  any  pipe  Or  reservoir  in 
which  a  given  pressure  is  maintained. 

inches  of 

water 

Feet  per  second 

Feet  per  minute 

.1 

29  04 

1256.40 

.2 

29.67 

1780  20 

•  3 

36.25 

2175.60 

.4 

41.86 

2511  60 

.5 

46.80 

2708.00 

.6 

51-26 

3075.60 

.7 

55  36 

3321.60 

.8 

69-10 

3546-00 

.9 

62.60 

3756.00 

1. 

66.14 

3968.40 

.1 

69.36 

4161-60 

•  2 

72.44 

4346.40 

3 

75  39 

4523.40 

.4 

78.21 

4692.60 

•  5 

80.96 

4857.60 

6 

83.59 

6015.40 

.7 

86-16 

5169.60 

.8 

88.65 

5319.00 

.9 

91.27 

5476-20 

2. 

93.42 

5605.20 

2-1 

95-72 

5743-20 

2  2 

97  96 

5877-60 

2  3 

100  15 

6009.00 

2.4 

102.29 

6137.40 

2  5 

104.39 

6263.40 

2  6 

106.43 

6385.80 

2.7 

108-46 

6507  60 

2.8 

110.43 

6625.80 

2.9 

112.37 

6742.20 

3. 

114.28 

6856-80 

8  1 

116.15 

6969.00 

3  2 

118  00 

7080.00 

3  3 

119.81 

7188.60 

84 

121.60 

7296.00 

8  •  5 

123.36 

7401.60 

Finally,  after  considering  the  change  of  velocity  that 
takes  place  when  the  density  changes  with  a  constant  tem- 
perature, let  the  temperature  change.  With  a  constant 
pressure,  the  volume  changes  with  the  absolute  temperature 
(460  +  t).  From  this  basis  the  values  given  in  the  second 


HEATING    AND    VENTILATION 


columns  of  Tables  XX  and  XXI,  which  were  figured  for  60 
degrees,  would  be  multiplied  by  the  relative  factors  for 
the  given  temperature  as  expressed  in  column  two,  Table 
XXII,  to  obtain  the  velocity  of  the  exhausting  air  at  any 
pressure  and  any  temperature.  Having  found  the  data 
from  Column  2,  find  other  points  of  information  concerning 
velocities,  pressures,  weights  and  horse  powers  in  moving 
air  by  multiplying  by  the  factors  as  given  in  the  respective 
columns. 

TABLE  XXII. 


Factor  for  rel- 

ip. in  degrees. 

ative    vel.     at 
same  pressure 
also    relative 
powers     to 
move      same 
vol.  of  air   at 
same  vel.  = 

Factor     for 
relative  pres- 
sure, also  wt. 
of  air  moved 
at  same  ve- 
locity = 

4600  4-  600 

Factor  for  rel- 
ative  vel.    to 
move     same 
wt.  of  air  also 
relative     pres- 
sure   to     pro- 
duce the  vel.  to 
move  same  wt. 

Factor  for  rel- 
ative power  to 
move      same 
wt.   of    air   at 
vel.  in  column 
4  and  pressure 
in  column  4  = 

§ 

VW1.  at  any  T 

T 

of  air  — 

factor    in   col- 
umn 4  squared 

H 

Wt.  at  4600  +  600 

1  -s-  Col.  3. 

80 

.97 

1.07 

.93 

.87 

40 

.98 

1.04 

.96 

.92 

50 

.99 

1.02 

.98 

.96 

60 

1.00 

1.00 

1.00 

00 

70 

1.01 

.98 

1.02 

.04 

80 

1-02 

.96 

1.04 

.08 

90 

1.03 

.94 

1  06 

.13 

100 

1.04 

.92 

1.09 

.19 

125 

1.06 

.89 

1-12 

-25 

150 

1.08 

.85 

1.18 

.39 

175 

1.10 

.82 

1.22 

1.49 

200 

1  13 

.79 

1.27 

1.61 

250 

1.17 

.73 

1.37 

1.88 

»X) 

1  21 

.68 

1.47 

2.16 

350 

1.25 

.64 

1.56 

2-43 

400 

1.28 

.60 

1.67 

2-79 

500 

1.36 

.54 

1.85 

8-42 

600 

1.48 

.49 

2.04 

4  16 

700 

1.49 

.45 

2.22 

4.93 

800 

1.56 

.41 

2.44 

5.95 

124.  Actual  Amount  of  Air  Exhausted: — When  air  of  any 
pressure  is  exhausted  from  one  receptacle  to  another  through 
an  orifice,  the  actual  velocity  remains  about  the  same  as 
the  theoretical  velocity,  being  slightly  reduced  by  friction, 
but  the  volume  of  air  discharged  is  greatly  reduced  because 


PLENUM    WARM    AIR    HEATING 


189 


of  the  contraction  of  the  stream  just  as  it  leaves  the  ori- 
fice. The  greatest  contraction  or  least  size  of  the  jet  is 
located  from  the  orifice  a  distance  of  about  one-half  the 
diameter  of  the  opening.  A  round  opening  is  the  most  effi- 
cient. Since  the  velocity  is  slightly  reduced  and  the  effec- 
tive area  of  the  opening  reduced  a  still  greater  amount,  the 
actual  amount  of  air  exhausted  in  any  given  time  will  be 
found  by  multiplying  the  theoretical  amount  by  a  constant 
which  is  the  product  of  the  coefficient  of  reduced  velocity 
and  the  coefficient  of  reduced  area.  From  tests  by  Weisbach 
the  following  approximate  values  are  quoted  by  the  Sturte- 
vant  Company  in  Mechanical  Draft,  page  152. 

Orifice  in  a  thin  plate,  .56 

.Short  cylindrical  pipe,  .75 

Rounded  off  conical  mouth  piece,  .98 

Conical  pipe,  angle  of  convergence 

about  6°,  .92 

125.  Results  of  Tests  to  Determine  the  Relation  be- 
tween Pressure  and  Velocity  in  Air  Transmission: — In  fan 
construction  the  number  of.  blades,  the  shape  of  the  blades, 
the  sizes  of  the  inlet  and  outlet  openings,  the  shape  and 
size  of  the  casement  around  the  blades  and  the  speed,  all 
have  an  effect  upon  the  relation  between  the  pressure  and 
the  velocity  of  the  air  discharge.  From  recent  tests  con- 
ducted in  the  Mechanical  Engineering  Department,  Univer- 
sity of  Nebraska,  the  curves  shown  in  Fig.  101,  a,  were  ob- 


J         2         3         4 

RATIO  OF  OPENING 

Fig.    lOla. 


.8         9 


ID 


HEATING  AND  VENTILATION 


2        .3         4        5        6 
RATD  OF  OPENING 

Fig.    lOlb. 


tained.  A  Number  2  Sirocco  blower  was  belted  to  an  elec- 
tric motor  and  delivered  air  to  a  horizontal,  circular  pipe 
whose  length  was  nine  times  the  diameter.  This  pipe  was 
provided  with  .reducing  nozzles  which  varied  the  area  of 
discharge  by  'tenths  from  full  opening  to  full  closed.  The 
air  tube  was  provided  also  with  manometer  tubes  for  static, 
dynamic  and  velocity  pressures,  arranged  with  an  adjustable 
scale  to  read  to  either  .01  or  .002  inch  of  water.  The  gross 
power  was  taken  by  wattmeter  and  the  delivered  power 
from  motor  to  fan  was  taken  by  dynamometer.  In  addition 
to  this,  the  frictional  horse-power  of  the  fan  and  motor 
unit  was  obtained  by  removing  the  fan  wheel  from  the 
shaft  and  taking  readings  with  all  other  conditions  remain- 
ing as  nearly  constant  as  possible.  The  friction  power, 
when  deducted  from  the  gross  power  recorded  by  the  watt- 
meter, gave  the  readings  for  the  net  horse-power  curve. 
A  galvanized  iron  intake,  enlarged  from  the  size  of  the 
fan  intake  to  a  rectangle  four  square  feet  in  area  and 
divided  up  by  fine  wires  into  rectangles  the  size  of  the 
standard  anemometer,  was  used  to  find  the  volume  of  air 
moved  per  minute.  This  volume  is  shown  in  the  curve 
C.  P.  M.  To  check  the  curve,  the  volume  was  calculated  for 
each  opening  by  the  Pitot  tubes  on  the  side  of  the  experi- 
mental pipe. 


PLENUM   WARM  AIR   HEATING  191 

To  fully  understand  this  article,  refer  to  Art.  15  and  note 
that  A,  Fig.  10,  registers  static  pressure  plus  velocity  pressure.  This 
sum  may  be  called  the  dynamic  pressure.  Also,  note  that  B  reg- 
isters only  static  pressure,  i.  e.,  that  pressure  which  acts  equally 
in  all  directions  and  serves  no  usefulness  in  .moving  the  air. 
Also,  note  that  A  —  B  =  C,  i.  e.,  dynamic  pressure  minus 
static  pressure  equals  velocity  pressure.  When  applied  in 
the  form  shown  by  C,  the  pressure  recorded  is  that  due  to 
the  velocity  only.  This  is  the  form  commonly  used.  Now 
referring  again  to  Fig.  101,  A.  V.  P.  is  that  pressure  re- 
corded by  C  when  applied  .to  the  air  current  at  the  fan  out- 
let, =  air  velocity  pressure.  P.  V.  P.  is  that  pressure  (ob- 
tained by  formulas  49  to  54)  that  would  be  shown  on  C  If 
the  air  were  moving  as  fast  as  the  tip  of  the  blades  on  the 
fan  wheel,  =  peripheral  velocity  pressure.  P.  V.  P.  =  1  dn 
Fig.  101,  &.  D.  P.  is  the  dynamic  pressure  and  would  be 
found  by  applying  A  only.  8.  P.  is  the  static  pressure  as 
stated  above. 

In  the  tests,  the  fan  was  run  at  constant  speed  and  the 
dynamic,  static  and  velocity  pressures  were  measured  about 
midway  of  the  pipe  at  full  opening.  Then  -the  openings  were 
changed  by  ten  per  cent,  reductions  until  the  pipe  was  fully 
closed  and  similar  readings  taken  for  each  reduction.  These 
readings  were  plotted  in  the  upper  set  of  curves.  Because 
of  the  fact  that  the  manometer  tubes  were  located  some 
distance  from  the  end  of  the  experimental  pipe,  there  was  a 
static  pressure,  ab,  recorded  at  full  opening.  This  caused 
the  dynamic  pressure  to  be  raised  a  corresponding  amount, 
a'  &'.  If  the  tubes  had  been  located  at  the  delivery  end  of 
the  pipe  the  static  and  dynamic  pressures  would  have  fallen 
from  &  and  &'  to  a  and  a'.  The  peripheral  velocity  of  the 
wheel  was  2828  feet  per  minute  and  the  corresponding  pres- 
sure, with  corrections  for  temperature,  was  found  by  formula 
52  to  be  .5  in.  of  water.  The  relation  between  this  peripheral 
velocity  pressure  and  the  air  velocity  pressure  is  shown  in 
the  lower  set  of  curves.  In  applying  the  lower  curves  to 
fan  practice  they  are  very  valuable  in  showing  the  relation 
between  the  velocity  of  the  wheel  circumference  and  that  of 
the  air  leaving  the  wheel.  Notice  that  the  relation  between 
the  observed  air  velocity  pressure  and  the  calculated  periph- 
eral velocity  pressure  at  full  opening  and  discharging  into 
free  air,  is  1.20  :  1.  Since  the  velocities  vary  as  the  square 
roots  of  the  pressures  (v  =  V2pfcT,  we  find  the  velocities  to 


192  HEATING  AND  VENTILATION 

be  V1.20  :  \/F  =  1.1  :  1.  That  is  to  say,  for  this  fan  the  air 
velocity  at  'the  free  opening  of  the  fan  is  1.1  times  the  per- 
ipheral velocity  of  the  wheel.  The  corresponding  velocity 
of  the  air  from,  the  average  steel  plate  fan  as  reported  by 
the  American  Blower  Company  and  as  shown  on  the  lower 
chart,  is  V.~45~  :  Vl~=  .67  :  1,  or  .61  of  the  speed  of  the 
Sirocco  fan  for  the  same  wheel  speed.  The  resistance  offered 
by  the  ducts  in  the  average  plenum  beating  system  is 
equivalent,  we  will  say,  to  that  offered  by  a  75  per  cent, 
gate  opening  in  the  experimental  pipe.  According  to  the 
diagrams  for  this  opening,  the  ratio  A.  V.  P.  to  P.  V.  P  is 
1.04  for  the  Sirocco  fan  and  .25  for  the  steel,  plate  fan.  The 
ratio  of  the  air  velocities  to  the  peripheral  velocities  then 
are,  respectively,  Vl704  :  Vl^=  1.02  :  1  and  VT2iT:  Vl~=  .5  :  1. 
These  show  that  with  a  75  per  cent,  opening  and  with  the 
fan  wheels  running  with  a  peripheral  velocity  of  3000  feet 
per  minute,  the  air  would  be  entering  the  ducts  at 
1.02  X  3000  =  3060,  and  .5  X  3000  =  1500  feet  per  minute 
respectively  for  the  two  types.  Conversely,  if  it  were  de- 
sired to  have  the  air  enter  the  ducts  at  1500  feet  per  minute, 
with  a  resistance  equivalent  to  a  75  per  cent,  opening,  the 
fan  wheels  would  have  peripheral  speeds  of  1500  -f-  1.02  = 
1470,  and  1500  -4-  .5  =  3000  feet  per  minute  respectively. 
From  these  we  obtain  the  wheel  diameter  for  any  given 
R.  P.  M.  Other  models  of  the  Sirocco  and  multiple  blade 
type  of  fans  show  less  variation  from  the  steel  plate  fan 
than  the  one  under  consideration.  It  will  be  seen  from  the 
above  that  the  late  change  in  construction  from  the  steel 
plate  type  to  the  multiple  blade  type  permits  a  smaller 
wheel  and  fan  to  be  installed  for  any  given  work.  This  can 
be  shown  to  be  a  desirable  change.  From  formula  61,  it  is 
seen  that  the  power  required  to  drive  a  fan  varies  as  the 
fifth  power  of  the  diameter  and  as  the  cube  of  the  speed. 
With  any  given  amount  of  air,  Q,  required  per  minute,  the 
power  will  be  reduced  very  greatly  by  reducing  the  diam- 
eter or  by  reducing  the  speed  of  the  fan.  Manufacturers' 
catalogs  should  be  consulted  for  capacities,  sizes,  etc.  Such 
tables  are  supplied  by  the  trade  in  form  for  easy  reference 
and  use. 

126.      "Work    Performed    and    Horse-Power    Consumed    in 
Moving^  Air: — The  foot  pounds  of  work  performed  in  moving  ' 
air  equals  the  product  of  the  moving  force  into  the  distance 


PLENUM    WARM    AIR    HEATING  193 

moved  through  in  any  given  time.  Let  pa  —  p&  =  p*  = 
moving  force  of  the  air  in  ounces  per  square  inch  and  A  = 
cross-sectional  area  of  current  in  square  inches.  Then  the 
pounds  per  square  inch  will  be  p*  -h  16,  and  the  foot  pounds 
of  work,  W,  and  the  horse-power,  //.  P.,  absorbed  per  min- 
ute by  the  current  of  air  in  being  moved,  will  be 

60  px  A  v 


16 


=  3.75  px  A  v  '(55) 


3.75  px  Av 

H.  P.  =  -  =  .000114  px  A  v  (56) 

33000 

This  formula  ma  7  be  stated  in  terms  of  the  cubic  feet  of 
air  discharged  per  minute.  Take  the  relation  between  p* 
and  hw  at  60  degrees  as  12  px  =  16  X  .433  Jiw;  also,  A  X  v  = 
144  Q'  when  Q'  =  cubic  feet  of  air  discharged  per  second 
and,  from  formula  54,  hw  =  v2  -j-  4356.  Then  by  substituting 
in  formula  56 

3.75   X  .577  X  v2  X  144  Q' 

H.P.=  -  —  .0000022  v2  Q'       (57) 
4356  X   33000 

APPLICATION  1.  —  Let  the  effective  area  of  a  stream  of  dry 
air  at  60  degrees,  exhausting  between  the  pressures  of  pa  = 
ll/2  ounces  and  p,  =  %  ounce,  be  400  square  inches.  What  is 
the  work  performed  per  minute  and  the  horse-power  con- 
sumed? (For  velocity  see  second  column  Table  XX). 

W  =  3.75  X  (1%  —  %)  X  400  X  87  =  130500  foot  pounds, 
and  H.  P.  =  .000114  X  (1%  —  %)  X  400  X  87  =  3.96. 

APPLICATION  2.  —  A  fan  is  delivering  1000000   cubic  feet  of 
aiir    per    hour    to    a    heating    system    with    a    pressure    o.f    % 
ounce.     What  is  the  theoretical  horse-power  of  the  fan? 
H.  P.  =  .0000022  X   (74.5)2  X   277  =  3.38 

127.  Actual  Horse-Power  Consumed  in  Moving  Air  by 
Blower  Fans:  —  The  theoretical  horse-power  of  a  fan  is  that 
horse-power  necessary  to  move  the  air.  This  amount  is  al- 
ways exceeded,  however,  because  of  the  inefficiency  of  the 
blower.  Let  E  —  efficiency  of  the  'blower,  then  formulas  5<6 
and  57  become 

.000114  px  A  v 

H.  P.  =  -  (58) 

E 

.0000022  v*  Q' 
H.  P.=-         —  -  (59) 


194  HEATING  AND  VENTILATION 

The  value  of  E  varies  with  the  peripheral  velocity  and 
the  percentage  of  free  outlet.  When  subjected  to  ordinary 
service,  the  efficiency  of  the  fan  or  blower  may  vary  any- 
where from  10  to  40  per  cent.  Probably  a  safe  figure,  for 
an  efficiency  not  definitely  known,  is  30  per  cent,  for  cen- 
trifugal fans  in  heating  systems.  Later  improved  types, 
such  as  the  Sirocco  and  Multivahe  fans,  will  be  found  from 
40  per  cent,  to  60  per  cent,  efficient.  See  also  Art.  131. 

128.  Carpenter's  Practical  Rules: — Many  experiments 
have  been  run  upon  blower  fans  to  determine  their  capacity 
in  cubic  feet  of  aiir  delivered  per  minute  and  to  determine 
the  horse-power  necessary  to  move  this  air.  Probably  as 
satisfactory  as  any  are  the  rules  quoted  by  Prof.  Carpenter 
in  H.  &  V.  B.,  Art.  162,  as  follows: 

Rule. — "The  capacity  of  fans,  expressed  in  cubic  feet  of  air  de- 
livered per  minute,  is  equal  to  the  cube  of  the  diameter  of  the  fan 
wheel  in  feet  multiplied  by  the  number  of  revolutions,  multiplied  by 
a  coefficient  having  the  following  approximate  value :  for  fan  with 
single  inlet  delivering  air  without  pressure,  0.6;  delivering  air  with 
pressure  of  one  inch,  0.5;  delivering  air  with  pressure  of  one  ounce, 
0.4;  for  fans  with  double  inlets,  the  coefficient  should  be  increased 
about  50  per  cent.  For  practical  purposes  of  ventilation,  the  ca- 
pacity of  a  fan  in  cubic  feet  per  revolution  will  equal  A  the  cube 
of  the  diameter  in  feet." 

Rule. — "The  delivered  horse-power  required  for  a  given  fan  or 
blower  is  equal  to  the  5th  power  of  the  diameter  in  feet,  multiplied 
by  the  cube  of  the  number  of  revolutions  per  second,  divided  by  one 
million  and  multiplied  by  one  of  the  following  coefficients  :  for  free 
delivery,  30;  for  delivery  against  one  ounce  pressure,  20;  for  de- 
livery against  two  ounces  of  pressure,  10." 

The  two  above  rules  stated  as  formulas  are  as  follows: 

ft.  of  air  per  min. 

(GO) 


C  X  R.  P.  M. 

where  D  —  the  diameter  in  feet  and  C  =  the  coefficient,  .4 
for  pressure  of  one  ounce,  .5  for  pressure  of  one  inch,  and 
.6  for  no  pressure. 

Z)5  (R.  P.  8.)*  X  C. 

H.P.= (61) 

1000000 

where  C  =  30  for  open  flow,  20  for  one  ounce  and  10  for  two 
ounces  pressure  respectively.  These  two  rules  may  be 


PLENUM    WARM    AIR    HEATING 


195 


checked  up  by  sizes  obtained  from  catalogs.  They  give, 
however,  in  ordinary  calculations,  very  close  approxima- 
tions. 

Note. — In  using  formula  60  for  Sirocco  or  Multivane 
fans,  the  coefficient,  C,  becomes  1.1,  1.2  and  1.3  respectively. 
Likewise,  for  formula  61  it  becomes  100,  95  and  90  respec- 
tively. 

129.  If  It  is  Desired  to  Obtain  the  Approximate  Sizes  of 
the  Different  Parts  of  the  Pan  Wheel  and  Opening,  the  same 
can  be  found  by  the  following  table  which  gives  good  aver- 
age values  for  steel  plate  fans.  For  more  complete  data 
see  tables  in  catalogs. 

TABLE  XXIII.* 


Diameter  wheel 

D 

Diameter  inlet,  single 

.66  D 

Diameter  inlet,  double 

.50  D 

Dimensions  of  exhaust 

.60  D 

X            .50 

D 

Width  of  wiheel  at  outer  circumference 

.50  D 

to     .60 

D 

Least  radial  distance  from  wheel  to  casing 

.08  D 

to     ,16 

D 

Maximum  radial  distance  from  wheel  to 

casing 

.50  D 

to   1.00 

D 

Least  side  distance  from  wheel  to  casing 

.05   D 

to     .08 

D 

Discharge  vert. 

Discharge  horiz. 

Occupied  space 

of 

Length 

1.7  D 

1.5  D 

full-housed  fan 

Width 

.7  D 

.1  D 

Height 

1.5  D 

1.7  D 

*This  table  does  not  apply  to  Sirocco  or  Multivane  fans. 

130.  Fan  Drives: — Fans  for  heating  and  ventilating 
purposes,  may  be  driven  >by  simple  horizontal  or  vertical, 
throttling  or  automatic  steam  engines,  or  by  electric  mo- 
tors; the  principal  advantage  of  the  latter  being  the  clean- 
liness. In  either  case  the  power  may  be  direct-connected 
or  belt-connected  to  the  fan.  Direct-connected  fans  make 
a  very  neat  arrangement,  but  they  require  slow  speed 
engines  or  motors,  occasionally  making  them  so  large  as  to 
be  prohibitive.  Where  engines  are  used,  any  unusual  noise 
or  pounding  in  the  parts  is  frequently  carried  through  the 
fan  to  the  air  current  and'  up  to  the  rooms.  Belted  drives 
may  run  at  higher  speeds  but  they  must  of  necessity  be  set 
off  from  the  fan  ten  feet  or  more  to  get  good  belt  contact. 


196  HEATING  AND  VENTILATION 

Chain  drives  that  are  fairly  quiet  in  operation  will  permit 
the  same  reductions  of  speed  and  will  allow  the  engine  to 
be  set  very  close  to  the  fan.  Where  a  reduction  is  made  in 
the  space  between  the  engine  and  the  fan,  it  had  best  be 
made  in  the  last  named  way. 

In  deciding  between  an  engine  drive  and  a  motor  drive 
for  use  with  steam  coils,  the  amount  of  steam  used  in  the 
engine  should  not  be  considered  a  loss,  since  this  is  all 
exhausted  into  the  heater  coils  and  is  used  instead  of  live 
steam  from  the  boilers.  An  engine  of  high  efficiency  is  not 
so  essential  either,  unless  the  exhaust  steam  cannot  be 
used.  Enclosed  engines  running  in  oil  are  preferred  when 
used  on  high  speeds.  The  belt  when  used  should,  if  pos- 
sible, have  the  tight  side  below  to  increase  the  arc  of 
contact. 

Electric  motors  have  more  quiet  action  and  in  special 
cases  should  be  specified.  They  would  generally  be  speci- 
fied for  installations  where  the  exhaust  steam  could  not 
be  used,  as  in  systems  for  ventilating  only.  This  method  of 
driving  the  fan  is  more  satisfactory  in  many  ways  but  its 
operation  is  usually  more  expensive.  Direct  current  motors 
are  desirable,  whenever  they  can  be  applied,  because  of  the 
convenience  in  obtaining  changes  of  speed  and  because  the 
motors  may  easily  be  direct-connected  to  the  fan.  Alter- 
nating current  motors  are  used  but  they  usually  run  at 
higher  speeds,  requiring  reduction  drives  and  are  not  so 
satisfactory  in  regulation.  Speed  reductions  of  40  per  cent, 
may  be  had  with  alternating  current  machines  where  re- 
quired. 

131.  Speed  of  the  Fan: — A  blower  fan,  exhausting  into 
the  open  air,  will  deliver  air  with  a  linear  velocity  slightly 
below  the  peripheral  velocity  of  the  fan  blades,  but  if  this 
same  fan  be  connected  to  a  system  of  ducts  and  heater 
coils,  the  linear  velocity  of  the  air  becomes  much  less  be- 
cause of  the  increased  resistance  and  the  lag  or  slip  that 
takes  place  between  the  fan  blades  and  the  moving  air.  In 
the  average  heating  system  this  slip  may  be  as  great  as 
40  to  50  per  cent.  See  Art.  127.  It  is  customary,  therefore, 
in  applying  blowers  to  heating  systems,  to  consider  the 
linear  velocity  of  the  air  as  it  leaves  the  fan  to  be  one- 
half  that  of  the  periphery  of  the  fan  blades.  Since  the 
velocity  of  the  air  upon  delivery  from  the  fan  should  not 
exceed  1800  to  2500  feet  per  minute,  the  outer  point  on  the 


PLENUM    WARM    AIR    HEATING 


197 


fan  blades  should  not  be  expected  to  move  faster  than  3600 
to  5000  feet  per  minute.  Knowing  this  peripheral  velocity, 
the  revolutions  per  minute  may  be  selected  and  the  diameter 
obtained. 

In  all  direct-connected  fans  the  revolutions  per  minute 
must  agree  with  that  of  the  engine  or  motor.  In  belted  fans, 
however,  this  restriction  need  not  apply.  It  is  found  that 
ordinary  blower  fans  running  at  high  speeds  are  very  noisy 
and  so  practice  has  determined  largely  the  number  of  revo- 
lutions to  use.  Speeds  used  by  the  American  Blower  Com- 
pany in  the  latest  type  of  Sirocco  fan  are  given  in  the  fol- 
lowing table. 

TABLE   XXIV. 
Speeds  of  Blower  Fans  in  R.  P.  M. 


Diameter  of 

Differential  pressures. 

wheel  in 

inches. 

1-2  oz.     |      8-4  oz. 

1  oz. 

1  1-2  oz. 

2oz. 

18 

638 

660 

762 

933 

1076 

24 

404 

495 

572 

700 

807 

33 

269 

330 

881 

466 

538 

48 

^202 

248 

286 

350 

403 

60 

161 

198 

228 

280 

322 

72 

184 

165 

190 

233 

269 

8i 

115 

142 

163 

200 

231 

90 

107 

132 

152 

186 

214 

In  the  recent  developments  for  blower  fans  the  num- 
ber of  blades  is  increased  and  the  depth  of  the  blades  is 
diminished,  making  the  operation  of  the  fan  somewhat  sim- 
ilar to  that  of  the  steam  turbine.  These  fans  seem  to  de- 
velop a  much  higher  efficiency  under  tests  than  the  ordi- 
nary paddle  wheel  fan.  As  a  result,  the  diameter  of  the 
w.heel  may  be  smaller  with  the  same  revolutions  for  a  given 
work  or  the  wheel  may  have  the  same  diameter  with  a  re- 
duced speed  for  a  given  work.  Tables  50,  51  and  52, 
Appendix,  give  a  summary  of  the  latest  catalog  data. 

132.      Size   of  the   Engine: — In   obtaining  the   size   of  the 


198  HEATING  AND  VENTILATION 

engine,  it  will  be  necessary  first  to  assume  the  horse-power. 
This  had  better  be  taken  as  a  certain-  ratio  to  that  of  the 
fan.  Probably  a  safe  value  would  be 

JET.  .P.  of  the  engine  =  |  //.  P.  of  the  fan  (62) 
Having  obtained  the  horse-power  of  the  engine,  it  will 
next  be  necessary  to  find  the  size  of  the  cylinder.  Let  p*  = 
the  absolute  initial  pressure  of  the  steam  in  the  cylinder, 
I.  e.,  atmospheric  pressure  +  gage  pressure,  and  r  =  number 
of  the  steam  expansions  in  the  cylinder,  i.  e.,  reciprocal  of 
the  per  cent,  of  cut-off.  The  cut-off  allowed  for  high  speed 
engines  in  economical  power  service,  approximates  25  per 
cent,  of  the  stroke,  but  in  engines  for  blower  work  this 
may  be  taken  at  50  per  cent,  or  half  stroke.  Find  the 
mean  effective  pressure,  PI,  by  the  formula 

1  +  hyperbolic  logarithm  of  r 

Pi  =  pa  — back  pressure    (63) 

r 

Next,  let  I  =  length  of  the  stroke  in  inches  and  2V  =  number 
of  revolutions  per  minute  and  apply  the  formula 

2  P!  I  A  N 

n.p.= (64) 

12   X   33000 

and  find  A,  the  area  of  the  cylinder,  from  which  obtain  rf. 
the  diameter  of  the  cylinder.  In  applying  formula  64  it 
will  be  necessary  to  assume  I.  This,  for  engines  operating 
blowers,  may  be  taken 

2   I  N  =  200  to  400 

Formula  63  assumes  that  the  steam  in  the  cylinder  expands 
according  to  the  hyperbolic  curve,  pv  =  p'v'.  For  values 
of  hyperbolic  or  Naperian  logarithms  see  Table  5,  Appendix. 
It  also  assumes  no  loss  in  the  recompression  of 
the  steam  in  the  cylinder.  Both  assumptions  are  only 
approximately  correct,  but  the  errors  are  slight  and  to  a 
certain  degree,  tend  to  neutralize  each  other,  hence  the 
final  results  from  this  formula  are  near  enough  to  be  used 
for  approximate  calculations.  For  such  work  as  this,  r 
may  be  taken  from  2  to  3,  the  former  being  probably  pre- 
ferred. The  back  pressure  should  not  be  taken  higher  than 
5  pounds  gage  (19.7  pounds  absolute),  since  this  is  deter- 
mined by  the  pressure  in  the  coils  carrying  exhaust  steam. 
This  pressure,  in  ordinary  service,  drops  nearly  to  atmos- 
pheric pressure. 


PLENUM    WARM    AIR    HEATING  19» 

lln  finding1  the  diameter  and  length  of  the  stroke  of  the 
cylinder,  it  may  'be  necessary  to  make  two  or  more  trial 
applications  before  a  good  size  can  be  obtained.  Owing 
to  the  fact  that  the  initial  steam  pressure  is  frequently 
low,  say  not  to  exceed  40  or  50  pounds,  the  mean  effective 
pressure  is  small,  thus  calling1  for  a  cylinder  of  large 
diameter.  In  such  cases,  the  diameter  of  the  cylinder  may 
be  greater  than  the  length  of  the  stroke.  In  cases  where 
high  pressure  steam  is  used,  say  100  pounds  gage,  the 
diameter  of  the  cylinder  would  be  less  than  the  length  of 
the  stroke. 

APPLICATION  1. — Assume  the  following  to  fit  the  design 
shown  in  Figs.  104,  105  and  106:  good  dry  steam  from  the 
boiler  to  the  engine  at  100  pounds  gage  pressure;  direct- 
connected  engine  to  fan,  running  at  180  revolutions  per 
minute  and  delivering1  2000000  cubic  feet  of  air  per  hour 
to  the  building;  steam  cut-off  in  the  cylinder  at  one-third 
stroke  and  used  in  the  coils  at  5  pounds  gage  pressure; 
find  the  sizes  and  horse-powers  of  the  fan  and  engine  unit. 
Applying  formulas  60,  61,  62,  63  and  64 


3/  2000000 

D.  of  fan  =   J  —  5.5   feet. 

\  60   X   1.1   X   180 

(5.5)BX  (3)3X  87 

H.  P.  of  fan  = =  11.8 

1000000 

Check  the  fan  size  and  horse-power  by  Table  52,  Appendix. 
H.  P.  of  Engine  =  A    X  11.8  =  15.7 

/      1  +   1.0986     \ 
Pi  =  115    f- J —    19.9    =    60.5     pounds    per 

250 

square  inch.     Now  if  2  I  N  =  250,  then  I  = =  .69  feet  = 

360 
15.7  X  12X  33000 

8.25    inches   and   A  =  —  =   34.5   square 

2  X  60.5  X  8.25  X  180 

inches  =  6.625   inches  diameter.     The  engine  would  be  6.625 
inches  X  8.25  inches,  at  180  R.  P.  M. 

APPLICATION  2. — Assuming1  the  values  as  in  application  1, 
excepting  that  the  steam  is  taken  from  a  conduit  main 
under  a  pressure  of,  say  30  pounds  per  square  inch  gage, 
that  2  I  N  —  300,  and  that  the  steam  cut-off  in  the  cylinder 
is  at  one-half  stroke.  Then,  as  before,  D  of  fan  =  5.5  feet; 


200  HEATING  AND  VENTILATION 

H.  P.  of  fan  =  11.7;  and  H.  P.  of  engine  =  15.7;  the  mean 
effective  pressure  is,  however, 

/       1   +    .6931        x 

p1  =  45    I    I  —  19.9  =  18.2  pounds  per  sq.   in. 

\  2  / 

15.7  X  12  X  33000 

and  A  =  • =  95   square  inches. 

2  X  18.2  X  10  X  180 

Size  of  engine  would  be  11  inches  X  10  inches,  at  180 
R.  P.  M. 

133.  Piping   Connections   around   Heater   and   Engine: — 

Where  the  fans  are  run  by  steam  power  it  is  considered 
best  to  reduce  the  pressure  of  the  steam  by  a  pressure  re- 
ducing valve  before  allowing  the  live  steam  to  enter  the 
coils.  Where  this  reduction  is  made  to  5  pounds  or  below, 
it  may  be  entered  into  the  same  main  with  the  exhaust 
steam  from  the  engine,  if  desired;  the  back  pressure  valve 
on  the  exhaust  steam  line  providing  an  outlet  to  the  at- 
mosphere in  case  the  pressure  should  run  above  the  5 
pounds  allowable  back  pressure.  If  the  value  of  the  back 
pressure  is  increased  much  above  5  pounds,  the  efficiency 
of  the  engine  is  seriously  affected.  In  many  installations 
where  the  condensation  from  the  live  steam  is  desired  free 
from  oil,  a  certain  number  of  coils  are  tapped  for  exhaust 
steam  and  this  condensation  trapped  to  a  waste  or  sewer, 
the  other  coils  delivering  to  a  receiver  of  some  sort  for 
boiler  feed  or  other  purposes  as  may  be  required. 

Every  system  should  be  fully  equipped  with  pressure 
reducing  valves,  back  pressure  valves,  traps  and  a  sufficient 
numiber  of  globe  or  gate  valves  on  the  steam  supply,  and  of 
gate  valves  on  the  returns  to  make  the  system  flexible  and 
responsive  to  varying  demands.  Figs.  102  and  103  show  a 
typical  plan  and  elevation  for  such  connections.  Some  en- 
gineers advocate  lifting  the  returns  about  20  or  30  inches 
as  shown  at  A  and  B  to  form  a  water  seal  for  each  sec- 
tion, thus  making  them  independent  in  their  action.  This, 
in  some  cases  where  the  coils  are  very  deep,  would  be  a 
benefit. 

134.  Application  to  School  Building: — The  three  follow- 
ing figures  and  summary   show   the   results   of  an   applica- 
tion   of    the    above    to    a    school    building.      The    summary, 


PLENUM    WARM    AIR    HEATING 


201 


Table  XXV,  gives  in  compact  form  such  calculated  results 
as  admit  of  tabulation.  Most  of  the  applications  through- 
out Chapters  X,  XI  and  XII,  also  refer  to  this  same  building. 
The  plans  show  the  double-duct  system,  with  plenum 
chamber  and  ducts  laid  just  below  the  basement  floor.  The 
small  arrows  show  the  heat  registers  and  vent  registers  for 
each  room.  The  same  stack  which  served  as  a  heat  car- 


Fig.  102. 


. 


TO  ATMOSPHERE 

BttK  PRESSURE  W.VE 


fe 


v--ctfE  wuw  ^ 
Fig.    103. 


rier  to  the  room  on  one  floor  serves  as  the  vent  stack 
for  the  corresponding  room  on  the  floor  above,  there  being 
a  horizontal  cut-off  between  them.  The  cut-off  at  the  heat 
register  should  be  so  curved  as  to  throw  the  current  of 
heated  air  into  the  room  with  the  least  possible  friction  or 
eddy  currents,  as  shown  in  Fig.  22. 


202 


HEATING   AND  VENTILATION 


TABLE  XXV. 
Data   Sheet  for  Figs.    104,    105,   106. 


Room 

n 

Heat  loss  in  B.t.u.  per 
hour  from  room  not 
counting  ventilation 

Heat  loss  counting  ex- 
posure 

Per  cent,  added 

Cubic  feet  of  air  needed 
per  hour  as  a  heat 
carrier 

No.  of  reg'ters  installed 

v,  -r. 

*2 

*1 

c3    > 
o>  o1 

S" 

«s 

tin 

33 

1- 

Size  of  registers  in 
inches 

Size  of  stack  in  inches 

I... 

X 
l1/, 

ll/2 
1% 
ll/2 

51,520 
74,200 
29,400 
86,260 
42,210 
85,350 

40,185 
57  876 

2 

322 

13x20 

13x13 

2 

8 

22,932 
^8,  288 
82,923 
27,573 

1 
1 
1 
1 

184 
226 
263 
220 

17x18 
17x21 
17x25 
17x21 

17x13 

17x18 
17x18 
17x18 

4... 

5 

6... 

7 

8     . 

ll/2 

16,520 

12,885 
12,885 
82,923 

1 

1 
1 

103 
103 
263 

13x13 
13x13 
17x25 

18x  8 
13x  8 
17x13 

9 

IT/ 
/3 

16,520 
42,210 

10 

Totals. 

844,190 

268,466 

11— 

13 

1  */£ 

11A 

ll/2 

11A 

1H 
1H 
VA 

81,130 
115,480 
40,500 
55,370 
68,840 
48,440 
51,940 
23,660 
28.fi60 
63,840 

63,281 
99,039 
31,775 
47,507 
51,775 
89,672 
40,518 
19,377 
18,455 
49,795 

2 
4 

1 
2 
2 
1 
2 
1 
1 
2 

506 
792 
278 
881) 
4S8 
817 
321 
155 
148 
89S 

17x24 
17x18 
17x26 
17x18 
17x21 
17x30 
13x20 
13x20 
.13x20 
17x18 

17x18 
17x18 
17x18 
17x18 
17x13 
17x13 
18x18 
13x18 
18x18 
17x18 

U 

126,973 
44,583 
60,907 
70,221 
50,862 

10 
10 
10 
10 
5 

18... 

14 

15  — 

16 

17  — 

18 

24,843 

5 

19  — 

?o  

Totals. 

540,100 

467,189 

21... 

1 
1 
1 
1 

1 
1 

Si 

1 

1 

81,130 
17,150 
103,460 
17,150 
81,900 
48,580 
98,080 
28,420 
87,380 
54,110 

63,281 
13,377 
88,764 
13,877 
27,447 
41,682 
79,819 
22,163 
29,156 
42,206 

2 
1 
2 
1 

1 
2 
2 
2 
1 
2 

5T6 
107 
710 
107 
220 
833 
638 
177 
233 
338 

17x24 
13x13 
'21x28 
13x13 
17x21 
13x20 
17x80 
13x15 
17x21 
13x20 

17x13 
18x  8 
17x18 
18x  8 
17x13 
13x18 
17x18 
13x  8 
17x18 
18x18 

22 

23... 
24  
25  
26  
27  
28  
29  
80  

113,800 

10 

85,189 
53,438 
102,333 

10 
10 
10 

Totals. 

598,961 

421,272 

Vent  registers  taken  same  size  as  heat  registers.    For  sizes  of 
engine,  fan,  heater  coils,  etc.,  see  applications  under  these  heads 


PLENUM    WARM    AIR    HEATING 


203 


;OE 


204 


HEATING  AND   VENTILATION 


SH 
PS 


=\  KH  fc=r5^i=i  >=i  bd 


J5     «f 


s 


Fig.  105. 


PLENUM  WARM  AIR  HEATING 


205 


MIT 

m 

•*.  a. 


Pig.   106. 


206  HEATING  AND   VENTILATION 

•i 

REFERENCES. 

References  on   Mechanical  Warm  Air  Heating:. 

TECHNICAL   BOOKS. 

Snow,  Furnace  Heating,  p.  99.  Monroe,  Steam  Heat,  d  Vent., 
p.  124.  Carpenter,  Heating  and  Ventilating  BiiiltJinfis,  p.  333. 
Hubbard,  Power,  Heating  and  Ventilation,  pages  525  and  551. 

TECHNICAL  PERIODICALS. 

Engineering  Review.  Ventilating  and  Air  Washing  Appar- 
atus Installed  in  the  Sterling- Welch  Building,  Cleveland, 
O.,  Jan.  1910,  p.  38.  Steam  Heat,  and  Vent.  Plant  Required 
for  Addition  to  the  Hotel  Astor,  New  York,  March  1910,  p. 
27.  Heating  and  Ventilating  Plant  of  the  Boston  Safe  De- 
posit and  Trust  Company's  Building,  C.  L.  Hubbard,  April 
1910,  p.  37.  Heating  and  Ventilating  Installation  on  the 
Burnet  St.  School,  Newark,  N.  J.,  Jan.  1909,  p.  20.  Heating 
and  Ventilating  the  New  Jersey  State  Reformatory,  Sept. 
1909,  p.  27.  Comparison  of  Heat,  and  Vent.  Plants  Installed 
in  Chicago  Schools  and  Buildings  at  Various  Periods,  T.  J. 
Waters,  June  1906,  p.  14.  Heating  and  Ventilating  of 
Schools,  F.  G.  McCann,  June  1906,  p.  11.  The  Heating  and 
Ventilation  of  Schools,  Dec.  1904,  p.  1;  March  1905,  p.  4; 
Sept.  1905,  p.  1;  Oct.  1905,  p.  5.  Note: — The  last  two  articles 
taken  together  comprise  a  complete  series  of  the  heating 
and  ventilating  of  the  schools  of  New  York  City.  Machinery. 
Fans,  C.  L.  Hubbard,  Oct.  1905,  p.  49;  Nov.  1905,  p.  109; 
Dec.  1905,  p.  165.  Heaters  for  Hot  Blast  and  Ventilation, 
C.  L.  Hubbard,  March  1907,  p.  353.  The  Heating  and  Ven- 
tilation of  Machine  Shops,  C.  L.  Hubbard,  Sept.  1907,  p.  1. 
Heating  and  Ventilating  Offices  in  Shops  and  Factories,  C. 
L.  Hubbard,  Feb.  1910,  p.  437.  Fans,  Machinery's  Reference 
Series,  No  39.  The  Heating  and  Ventilating  Magazine,  Figuring 
Flow  of  Air  in  Metal  Pipes  by  Chart,  B.  S.  Harrison,  Dec. 
1905,  p.  1.  Flow  of  Air  in  Metal  Pipes,  J.  H.  Kinealy,  July 
1905,  p.  3.  Friction  of  Bends  in  Air  Pipes,  J.  H.  Kinealy, 
Sept.  1905,  p.  1.  A  Test  of  Hot  Blast  Heating  Coils,  March 
1905,  p.  1.  Simplifying  the  Installation  and  Operation  of 
School  Heating  and  Ventilating  Apparatus,  S.  R.  Lewis,  July 
1908,  p.  10.  A  Rational  Formula  Covering  the  Performance 
of  Indirect  Heating  Surface,  Perry  West,  March  1909,  p.  1. 
Charts  Showing  the  Performance  of  Hot  Blast  Coils,  B.  "S. 
Harrison,  Oct.  1907,  p.  23.  Loss  of  Pressure  In  Blowing  Air 
through  Heater  Coils,  with  New  Formula,  E.  M.  Shealy, 
Nov.  1911.  The  Engineering  Magazine.  Modern  Systems  for 
the  Ventilation  and  Tempering  of  Buildings,  Percival-  R. 
Moses,  Feb.  1908.  Domestic  Engineering.  Practical  Sugges- 
tions about  Blower  Systems  for  Shop  Heating,  F.  R. 
Still,  Vol.  46.  No.  4,  Jan.  23,  1909,  p.  100;  Vol.  46,  No. 
5,  Jan.  30,  1909,  p.  125.  Trans.  A.  8.  H.  &  V.  E.  Supplementing 
Direct  Radiation  by  Fans,  Vol.  X,  p.  286.  Methods  of  Test- 


PLENUM  WARM  AIR  HEATING-  207 

ing  Blowing  Fans,  R.  C.  Carpenter,  Vol.  VI,  p.  69.  Some 
Experiments  with  the  Centrifugal  Fan,  W.  S.  Monroe,  Vol. 
V,  p.  117.  The  Metal  Worker.  Heating  and  Ventilating  Willard 
Parker  Hospital,  New  York,  July  6,  1907,  p.  43.  New  Yo.rk  Stock 
Exchange.  Aug.  5,  1905.  p.  55.  Fans,  serial  article  beginning 
May  2,  1908,  p.  44.  Heating  and  Ventilating  a  Factory,  Sept. 
12/1908,  p.  45.  Obviating  Noise  in  Fan  Systems,  serial  begin- 
ning Oct.  31,  1908,  p.  52.  Heating  Messiah  Home,  Fordham,  N. 
Y.,  Nov.  21,  1908,  p.  37.  Filters  for  Air  Supply,  serial  begin- 
ning Nov.  28,  1908,  p.  44.  Heating  Christian  Science  Church, 
Boston,  May  9,  1908,  p.  35.  Ventilation  by  Individual  Air  Ducts, 
Frederick  Bass,  June  7,  1912.  Railway  Age  Gazette.  Heating  Plant 
for  Mill,  Nov.  13,  1908,  p.  1369.  The  Engineering  Record.  A 
Formula  for  Indirect  Heating,  Dec.  13,  1909.  Temperatures 
for  Testing  Indirect  Heating  Systems,  W.  W.  Macon,  Feb.  2, 
1907,  p.  135.  Performance  of  Hot  Blast  Heating  Coils,  Jan. 
28,  1905.  Some  Features  of  Indirect  Heating,  May  27,  1905. 
Heating  and  Ventilating  in  the  Carnegie  Residence,  N.  Y., 
Oct.  3,  1903.  Vol.  48,  p.  403.  Ventilating  and  Heating  the 
Rochester  Athenaeum  &  Mechanics  Institute,  July  19,  1902. 
Vol.  46,  p.  60.  Poiccr.  Horse-Power  of  a  Fan  Blower,  Alibert 
E.  Guy,  June  13,  1911.  Heating  and  Ventilating  System  of 
the  Ritz-Carlton  Hotel,  Charles  A.  Fuller,  Mar.  19,  1912. 
Ventilating  System  for  Small  Schools,  Charles  A.  Fuller, 
Dec.  10,  1912. 


CHAPTER  XIII. 


DISTRICT     HEATING     OR     CENTRALIZED     HOT     WATER 
AND   STEAM  HEATING. 


GENERAL. 

135.  Heating:  Residences  and  Business  Blocks  from  a 
central  station  is  a  method  that  is  being  employed  in  many 
cities  and  towns  throughout  the  country.  The  centralization 
of  the  heat  supply  for  any  district  in  one  large  unit  has  an 
advantage  over  a  number  of  smaller  units  in  being  able  to 
burn  the  fuel  more  economically,  and  in  being  able  to  re- 
duce labor  costs.  It  has  also  the  advantage,  when  in  con- 
nection with  any  power  plant,  of  saving  the  heat  which 
would  otherwise  go  to  waste  in  the  exhaust  steam  and  stack 
gases,  by  turning  it  into  the  heating  system.  The  many 
electric  lighting  and  pumping  stations  around  the  country 
give  large  opportunity  in  this  regard.  Since  the  average 
steam  power  plant  is  very  wasteful  in  these  two  particulars, 
any  saving  that  might  be  brought  about  should  certainly  be 
sought  for.  On  the  other  hand,  however,  a  plant  of  this 
kind  has  t.he  disadvantage  in  that  it  necessitates  transmit- 
ting the  heating  medium  through  a  system  of  conduits,  which 
generally  is  a  wasteful  process.  The  failure  of  many  of  the 
pioneer  plants  has  cast  suspicion  upon  all  such  enterprises 
as  paying  investments,  but  the  successful  operation  of  many 
others  shows  the  possibilities,  where  care  is  exercised  in 
their  design  and  operation. 

136.  Important  Considerations  in  Central  Station  Heat- 
ing:— In  any  central  heating  system,  the  following  consider- 
ations will  go  far  towards  the  success  or  the  failure  of  the 
enterprise: 

First. — There  should  be  a  demand  for  the  heat. 

Second. — The  plant  should  be  near  to  the  territory  heated. 

Third. — There  should  be  good  coal  and  water  facilities  at 
the  plant. 

Fourth. — The  quality  of  all  the  materials  and  the  instal- 
lation of  the  same,  especially  in  the  conduit  concerning  in- 


DISTRICT   HEATING  209 

sulation,  expansion  and  contraction,  and  durability,  are 
points  of  unusual  importance. 

Fifth. — The  plant  must  be  operated  upon  an  economical 
basis,  the  same  as  is  true  of  other  plants. 

Sixth. — The  load-factor  of  the  plant  should  be  high.  This 
is  one  of  the  most  important  points  to  be  considered  in  com- 
bined heating1  and  power  work.  The  greater  the  proportion 
of  hours  each  piece  of  apparatus  is  in  operation,  to  the  total 
number  of  hours  that  the  plant  is  run,  the  greater  the  plant 
efficiency.  The  ideal  load-factor  requires  that  all  of  the  ap- 
paratus be  run  at  full  load  all  the  time. 

The  average  conduit  radiates  a  great  deal  of  heat,  hence, 
the  nearer  the  plant  to  the  heated  district  the  greater  the 
economy  of  the  system.  Likewise  a  location  near  a  railroad 
minimizes  fuel  costs,  and  good  water,  with  the  possibility 
of  saving  the  water  of  condensation  from  the  steam,  assists 
in  increasing  ^the  economy  of  the  plant.  It  is  to  be  expected 
that  even  a  well  designed  plant,  unless  safeguarded  against 
ills  as  above  suggested,  would  soon  succumb  to  inevitable 
failure. 

Two  types  of  centralized  heating  plants  are  in  use,  hot 
water  and  steam.  Each  will  be  discussed  separately.  In  the 
discussion  of  either  system,  certain  definite  conditions  will 
have  to  be  met.  First  of  all,  there  should  be  a  demand  in 
that  certain  locality  for  such  a  heating  system,  before  the 
plant  can  be  considered  a  safe  investment.  To  create  a  de- 
mand requires  good  representatives  and  a  first-class  resi- 
dence or  business  district.  When  this  demand  is  obtained 
the  plan  of  the  probable  district  to  be  heated  will  first  be 
platted  and  then  the  heating  plant  will  be  located.  In  many 
cases  the  heating  plant  will  be  an  added  feature  to  an  al- 
ready established  lighting  or  power  plant  and  its  location 
will  be  more  or  less  a  predetermined  thing. 

In  addition  to  these  material  and  financial  features  just 
mentioned,  one  must  consider  the  legal  phases  that  always 
come  up  at  such  a  time.  These  relate  chiefly  to  the  franchise 
requirements  that  must  be  met  before  occuping  the  streets 
with  conduit  lines,  etc.  All  of  these  considerations  are  a 
part  of  the  one  general  scheme. 

137.  The  Scope  of  the  Work  in  central  station  'heating 
may  be  had  from  the  following  outline: 


210 


HEATING  AND  VENTILATION 


fHot  Water  Heating 
by  use  of 


Central  Sta- 
tion Heating-* 


Exhaust  steam  heater* 
Live  steam  heaters 
Heating  boilers 
Economizers 
Injectors  or 
Com-minglers 


Steam  Heating f  Exhaust  steam 

\Live  steam 


In  the  hot  water  system  the  return  water  at  a  lowered  tem- 
perature enters  the  power  plant,  is  passed  through  one  or 
more  pieces  of  apparatus  carrying  live  or  exhaust  steam,  or 
flue  gases,  and  is  raised  in  temperature  again  to  that  in  the 
outgoing  main.  From  the  above,  a  number  of  combinations 
of  reheating  can  be  had.  Any  or  all  of  the  units  may  be  put 
in  one  plant  and  the  piping  system  so  installed  that  the 
water  will  pass  through  any  single  unit  and  out  into  the 
main;  or,  the  water  may  be  split  and  passed  through  the 
units  in  parallel;  or,  it  may  be  made  to  pass  through  the 
units  in  series.  All  of  these  combinations  are  possible,  but 
not  practicable.  In  most  plants,  two  or  three  combinations 
only  are  provided.  In  the  existing  plants  the  order  of  pref- 
erence seems  to  be,  exhaust  steam  reheaters,  economizers, 
heating  boilers,  injectors  or  com-minglers,  and  live  steam 
heaters. 

All  of  the  above  pieces  of  reheating  apparatus  .operate 
by  the  transmission  of  heat  through  metal  surfaces,  such  as 
brass,  steel  or  cast  iron  tubes,  excepting  the  com-mingler, 
this  being  simply  a  barometric  condenser  in  which  the  exhaust 
steam  is  condensed  by  the  injection  water  from  the  return 
main,  the  mixture  being  drawn  'directly  into  the  pumps. 

The  objection  to  the  tube  transmission  is  the  lime,  mud 
and  oil  deposit  on  the  tube  surfaces,  thus  reducing  the  rate 
of  transmission  and  requiring  frequent  cleaning.  The  ob- 
jections to  the  com-minglers  are,  first,  that  the  pump  must 
draw  hot  water  from  the  condenser  and  second,  that  a  cer- 
tain amount  of  the  oil  passes  into  the  heating  line.  With 
perfected  apparatus  for  removing  the  oil,  the  com-mingler 
will  no  doubt  supersede,  to  a  large  degree,  the  tube  re- 
heaters  in  hot  water  heating. 


DISTRICT   HEATING  2ll 

In  the  steam  system  the  proposition  is  very  much  simpli- 
fied. The  exhaust  steam  passes  through  one  or  more  oil 
separating  devices  and  is  then  piped  directly  to  the  header 
leading  to  the  outgoing  main.  Occasionally  a  connection  is 
made  from  this  line  to  a  condenser,  such  that  the  steam, 
when  not  used  in  the  heating  system,  may  be  run  directly 
to  the  condenser.  These  pipe  lines,  of  course,  are  all  prop- 
erly valved  so  that  the  current  of  steam  may  easily  be  de- 
flected one  way  or  the  other.  In  addition  to  this  exhaust 
steam  supply,  live  steam  is  provided  from  the  boiler  and 
enters  the  header  through  a  pressure  reducing  valve.  .  In 
any  case  when  the  exhaust  steam  is  insufficient  the  supply 
may  be  kept  constant  by  automatic  regulation  on  the  reduc- 
ing valve. 

In  selecting  between  hot  water  and  steam  systems  the 
preference-  of  the  engineer  is  very  largely  the  controlling1 
factor.  The  preference  of  the  engineer,  however,  should  be 
formed  from  facts  and  conditions  surrounding  the  plant,  and 
should  not  come  from  mere  prejudice.  The  following  points 
are  some  of  the  important  ones  to  be  considered: 

First  cost  of  plant  installed. — This  is  very  much  in  favor  of 
the  steam  system  in  all  features  of  the  power  plant  equip- 
ment, the  relative  costs  of  the  conduit  and  the  outside  work 
being  very  much  the  same  in  the  two  systems. 

Cost  of  operation. — This  is  in  favor  of  the  hot  water  sys- 
tem because  of  the  fact  that  the  steam .  from  the  engines 
may  be  condensed  at  or  below  atmospheric  pressure,  while 
the  exhausts  from  the  engines  in  the  steam  systems  must 
be  carried  from  five  to  fifteen  pounds  gage,  which  naturally 
throws  a  heavy  back  pressure  upon  the  engine  piston. 

Pressure  in  circulating  mains. — This  is  in  favor  of  the  steam 
system.  The  pressure  in  any  steam  radiator  will  be  only 
a  few  pounds  above  atmosphere,  while  in  a  hot  water  sys- 
tem, connected  to  high  buildings,  the  pressure  on  the  first 
floor  radiators  near  the  level  of  the  mains  becomes  very 
excessive.  The  elevation  of  the  highest  radiator  in  the 
Circuit,  therefore,  is  one  of  the  determining  factors. 

Regulation. — It  is  easier  to  regulate  the  hot  water  system 
without  the  use  of  the  automatic  thermostatic  control,  since 
the  temperature  of  the  water  is  maintained  according  to  a 
schedule,  which  fits  all  degrees  of  outside  temperature. 


212  HEATING  AND  VENTILATION 

When  automatic  control  is  applied,  this  advantage  is  not  so 
marked. 

Returning  the  water  to  the  power  plant.— In  most  steam  plants 
the  water  of  condensation  is  passed  through  indirect  heaters, 
to  remove  as  much  of  the  remaining  heat  as  possible  and 
is  then  run  to  the  sewer.  This  procedure  incurs  a  consider- 
able loss,  especially  in  cold  weather  when  the  feed  water 
at  the  power  plant  is  heated  from  low  temperatures.  This 
point  is  in  favor  of  the  hot  water  system. 

Estimating  charges  for  heat. — This  is  in  favor  of  the  steam 
system  since,  by  meter  measurement,  a  company  is  able  to 
apportion  the  charges  intelligently.  The  flat  rate  charged 
for  water  heating  and  for  some  steam  heating  is  in  many 
cases  a  decided  loss  to  the  -company. 

138.  Conduits: — 0!n  installing  conduits  for  .either  hot 
water  or  steam  systems  the  selection  should  be  made  after 
determining,  first,  its  efficiency  as  a  heat  insulator;  second, 
its  initial  cost;  third,  its  durability.  Other  points  that  must 
be  accounted  for  as  being  very  essential  are:  the  supporting, 
anchoring,  grading  and  draining  of  the  mains;  provision  for 
expansion  and  contraction  of  the  mains;  arrangements  for 
taking  off  service  lines  at  points  where  there  is  little  move- 
ment of  the  mains;  and  the  draining  of  the  conduit. 

Some  conduits  may  be  installed  at  very  little  cost  and 
yet  may  be  very  expensive  propositions,  because  of  their  in- 
ability to  protect  from  heat  losses;  while,  on  the  other  hand, 
some  of  the  most  expensive  installations  save  their  first 
cost  in  a  couple  of  years'  service.  Many  different  kinds  of 
insulating  materials  are  used  in  conduit  work  such  as  mag- 
nesia, asbestos,  hair  felt,  wool  felt,  mineral  wool  and  air  cell. 
Each  of  these  materials  has  certain  advantages  and  under 
certain  conditions  would  be  preferred.  It  is  not  the  real 
purpose  here  to  discuss  the  merits  of  the  various  insulators, 
because  the  quality  of  the  workmanship  in  the  conduit  en- 
ters into  the  final  result  so  largely.  The  different  ways  that 
pipes  may  be  supported  and  insulated  in  outside  service  will 
be  given,  with  general  suggestions  only.  Fig.  107  shows  a 
few  of  the  many  methods  in  common  use.  A  very  simple 
conduit  is  shown  at  A.  This  is  built  up  of  wood  sections 
fitted  end  to  end,  then  covered  with  tarred  paper  to  prevent 
surface  water  leaking  in  and  bound  with  straps.  The  pipe 
either  is  a  loose  fit  to  the  bore  and  rests  upon  the  inner  sur- 


DISTRICT   HEATING  213 

face,  or  is  supported  on  metal  stools,  driven  into  the  wood  or 
merely  resting  upon  it.  These  stools  hold  the  pipe  concen- 
tric with  the  inner  bore  of  the  log.  With  much  movement 
of  the  pipe  endwise,  from  expansion  and  contraction,  these 
stools  should  not  be  used  unless  they  are  loose  and  have  a 
wide  surface  contact  with  the  wood.  A  metal  lining  with 
the  pipe  resting  directly  upon  it  is  considered  good.  The 
conduit  is  laid  to  a  good  straight  run  in  a  gravel  bed  and 
usually  over  a  small  tile  drain  to  carry  off  the  surface  water, 
excepting  as  this  drain  is  not  necessary  in  sections  where 
there  is  good  gravel  drainage.  The  insulation  in  A  is  only 
fair.  The  air  space  around  the  pipe,  however,  is  to  be  com- 
mended. B  is  an  improvement  over  A  and  is  built  up  of 
boards  notched  at  the  edges  to  fit  together.  The  materials 
used,  from  the  outside  to  the  center,  are  noted  on  the  sketch 
beginning  with  the  top  and  reading  down.  This  covering  is 
in  general  use  and  gives  good  satisfaction  from  every  stand- 
point. C  shows  a  good  insulation  and  supports  the  pipe 
upon  rollers  at  the  center  of  a  line  of  halved,  vitrified  tile. 
The  lower  half  of  the  tile  should  be  graded  and  the  pipe  then 
run  upon  the  rollers,  after  which  it  may  be  covered  with 
some  prepared  covering  and  the  remaining  space  next  the 
tile  filled  with  asbestos,  mineral  wool  or  other  like  material. 
D  shows  the  same  adapted  to  cellar  work.  Occasionally  two 
pipes  are  run  side  by  side,  main  and  return,  in  which  case 
large  halved  tiles  may  be  used  as  in  E,  having  large  metal 
supports  curved  on  the  lower  face  to  fit  the  tile.  If  these 
supports  are  not  desired  the  same  kind  of  straight  tiles  may 
be  used  with  a  tee  tile  inserted  every  8  to  12  feet  having  the 
bell  looking  down  as  in  F.  In  this  bell  is  built  a  concrete 
setting  with  iron  supports  for  the  pipes  which  run  on  rollers, 
over  a  rod.  These  rollers  are  sometimes  pieces  of  pipes  cut 
and  reamed,  but  are  better  if  they  are  cast  with  a  curvature 
to  fit  the  pipes  to  be  supported.  This  form  of  conduit,  when 
drained  to  good  gravel,  gives  first-class  service.  O,  H  and  / 
show  box  conduits  with  two  or  more  thicknesses  of  %  inch 
boards  nailed  together  for  the  sides,  top  and  bottom.  The 
bottom  of  the  conduit  is  first  laid  and  the  pipe  is  run.  The 
sides  are  then  set  in  place  and  the  insulating  material  put 
in,  after  which  the  top  is  set  and  the  whole  filled  in.  /  shows 
the  best  form  of  box,  since  with  the  air  spaces  this  is  a 
very  good  insulator.  All  wood  boxes  are  very  temporary, 
hence,  brick  and  concrete  are  usually  preferred.  K  is  a 


214 


HEATING   AND   VENTILATION 


GRAVEL 
-PUMP  LOG 

'STOOLS 

>PIPE   - 
DRAIN 


GRAVEL 

-A5PHALTUM    J 
WOOD 

COR 

ASBESTOS 

TIN   LINING 
MIN    WOOL- 
PIPE 
ROLLER 


WOOD 
TILE 

MIN. WOOL 
SECTIONAL 

COVERING; 
PIPE 
ROLLER 


GRAVEL 

TILE 

MIN     WOOL 

PIPE 

PIPE    5UPR 
CONCRETE 

DRAIN 


Fig.  107a. 


DISTRICT    HEATING 


215 


TONE 
RICK 

MIN    WOOL 
^A/OOD 


INSULATION  ] 


ROLLER— 7 
GRAVEL 
DRAIN 


GRAVEL 

WOOD 

-INSULATION 
PIPE 

ROLLER 


i  SLATE/ 

'      CEMENT/ 


;MALVED  TILE; 


EC  COVERING; 
PIPE 


Fig.  107b. 


216  HEATING  AND  VENTILATION 

conduit  with  8  inch  brick  walls  covered  with  flat  stones  or 
halved  glazed  tiles  cemented  to  place  to  protect  from,  sur- 
face leakage.  The  bottom  of  the  conduit  has  supports  built 
in  every  8  to  12  feet,  and  between  these  points  the  conduit 
drains  to  the  gravel.  The  usual  rod  and  roller  here  serve 
as  pipe  supports.  The  pipe  is  covered  with  sectional  cover- 
ing and  the  rest  of  the  space  may  or  may  not  be  filled  with 
wool  or  .chips,  as  desired.  L  shows  the  sectional  covering 
omitted  and  the  entire  conduit  filled  with  mineral  wool,  hair 
felt  or  asbestos,  and  ashes.  M  has  the  supporting  rod  built 
into  the  sides  of  the  conduit  and  has  the  bottom  of  the  con- 
duit bricked  across  and  cemented  to  carry  the  leaks  and 
drainage  to  some  distant  point.  N  shows  a  concrete  bot- 
tom with  brick  sides,  having  the  pipe  supported  upon  cast 
iron  standards.  The  latest  conduit  has  concrete  slabs  for 
bottom  and  sides  and  has  a  reinforced  concrete  slab  top. 
This  comes  as  near  being  permanent  as  any,  is  reasonable 
in  price,  and  when  the  interior  is  filled  with  good  non-con- 
ducting material,  or  when  the  pipe  is  covered  with  a  good 
sectional  covering,  it  gives  fairly  high  efficiency. 

All  conduits  should  be  run  as  nearly  level  as  possible 
to  avoid  the  formation  of  air  and  water  pockets  in  the  main. 
Any  unusual  elevation  in  any  part  of  the  main  may  require 
an  air  vent  being  placed  at  the  uppermost  point  of  the  curve, 
otherwise  air  may  collect  in  such  quantities  as  to  retard  cir- 
culation. All  low  points  in  the  steam  lines  must  be  drained 
to  traps. 

The  heat  lost  from  conduits  is  an  item  of  considerable  im- 
portance. A  good  quality  of  materials  and  insulation  will 
probably  reduce  this  loss  as  low  as  20  to  25  per  cent,  of 
the  amount  lost  from  the  bare  pipe.  To  show  the  method  of 
analysis  and  to  obtain  an  estimate  of  the  average  conduit 
losses,  the  following  application  will  be  made  to  a  supposed 
two-pipe  hot  water  system.  The  loss  of  heat  in  B.  t.  u.  per 
lineal  foot  from  any  pipe  per  hour  may  be  taken  from  the 
formula 

He  =  KCA   (t  —  /')  (65) 

where  K  =  rate  of  transmission  for  uncovered  pipes,  C  =  100 
per  cent.  —  efficiency  of  the  insulation,  A  =  area  of  pipe  sur- 
face per  lineal  foot  of  pipe,  t  =  average  temperature  in  the 


DISTRICT   HEATING 


217 


inside  of  the  pipe  and  t'  =  average  temperature  on  the  out- 
side of  the  conduit. 

APPLICATION. — Having  given  a  system  of  conduit  pipes 
(two  pipes  in  one  conduit)  with  sizes  and  lengths  as  stated 
in  the  firs"t  and  second  columns  of- Table  XXVI,  what  is  the 
probable  heat  loss  in  B.  t.  u.  per  hour  on  a  winter  day  and 
what  is  the  radiation  equivalent  in  a  hot  water  system  car- 
rying water  at  an  average  temperature  of  170  degrees? 


TABLE  XXVI. 


Pipe  size 
inches 

Total  lineal 
feet  of  main 
and  return 

Surface  per 
foot  of  length 
A 

B.  t.  u.  per  hr. 
per  lineal  foot 
He 

Equivalent 
no.  of  sq.ft. 
of  H.W.  Rad. 

2 

5000 

.62 

.48.8 

1435 

3 

2000 

.91 

71.6 

842 

4 

3000 

1.06 

83.4 

1472 

6 

3000 

1.73 

137.1 

2420 

8 

2000 

2.26 

177.9 

2093 

10 

.  2000 

2.83 

221.9 

2611 

12 

2000 

3.33 

262.0 

3082 

14 

1000 

4.00 

314.8 

1852 

Totals.     B.  t.  u.  lost  per  hour  2687100 


15807 


If  K  —  2.25,  C  =  100  —  75  =  25  per  cent.,  *  =  175  and 
f  =  35,  we  have  for  a  2  inch  pipe,  He  =  2.25  X  .25  X  .62  X  140 
=  48.8,  which  for  5000  lineal  feet  =  244000  B.  t.  u.,  and  for 
the  entire  system  2687100  B.  t.  u.  If  each  square  foot  of  hot 
water  radiation  gives  off  170  B.  t.  u.  per  hour  then  the 
radiation  equivalent  for  the  2  inch  pipe  is  244000  -T-  170  = 
1453  square  feet.  Similarly  work  out  for  each  pipe  size  and 
obtain  the  values  given  in  the  last  column  of  the  table.  This 
conduit  loss  is  sufficient  to  heat  15807  square  feet  of  radia- 
tion in  the  district.  In  terms  of  the  coal  pile  it  approxi- 
mates 350  pounds  per  hour.  Now  assuming  the  14  inch 
main  to  supply  the  entire  district  at  a  velocity  of  6  feet  per 
second  we  have  approximately  162000  square  feet  of  H.  W. 
surface  on  the  line.  From  this  the  line  loss  is  15807-7-162000 
=  9.1  per  cent.  It  should  be  remembered  that  the  above  as- 
sumes the  plant  working  under  a  heavy  load  when  the  per 
cent,  of  line  loss  is  a  minimum.  This  loss  remains  fairly 


218  HEATING  AND   VENTILATION 

constant  while  the  heat  utilized  in  the  district  fluctuates 
greatly.  In  mild  weather,  therefore,  the  per  cent,  of  line 
loss  to  the  total  heat  transmitted  is  much  greater. 

139.  Layout  of  Street  Mains  and  Conduits: — No  definite 
information  can  be  given  concerning  the  layout  of  street 
mains,  because  the  requirements  of  each  district  would  call 
for  independent  consideration.  The  following  general  sug- 
gestions, however,  can  be  noted  as  applying  to  any  hot 
water  or  steam  system: 

Streets  to  ~be  used. — Avoid  the  principal  streets  in  the  city, 
especially  those  that  are  paved;  alleys  are  preferred  because 
of  the  minimum  cost  of  installation  and  repairs. 

Cutting  of  the  mains. — Do  not  cut  the  main  trunk  line  for 
branches  more  often  than  is  necessary.  Provide  occasional 
by-pass  lines  between  the  main  branches  at  the  most  im- 
portant points  in  the  system,  so  that,  if  repairs  are  being 
made  on  any  one  line,  the  circulation  beyond  that  point  may 
be  handled  through  the  by-pass.  Such  by-pass  lines  should 
be  valved  and  used  only  in  case  of  emergency. 

Offsets  and  expansion  joints. — Offsets  in  the  lines  hinder 
the  free  movement  of  the  water  and  add  friction  head  to  the 
pumps;  hence,  in  water  systems,  the  number  should  be  re- 
duced to  a  minimum.  Long  radius  bends  at  the  corners  re- 
duce this  friction.  Offsets  are  especially  valuable  to  take 
•up  the  expansion  and  contraction  of  the  piping  without  the 
aid  of  expansion  joints.  This  is  illustrated  in  Fig.  108,  where 
anchors  are  placed  at  A,  and  the  gradual  bending  of  the 
pipes  at  each  corner  makes  the  necessary  allowance.  The 
expansion  in  wrought  iron  is  about  .OOOOS  inch  per  foot  per 
degree  rise  in  temperature;  hence  in  a  hot  water  main  the 
linear  expansion  between  0°  and  212"  is  .017  inch  per  foot  of 
length  or  1.7  inches  for  each  100  feet  of  straight  pipe.  In 
hot  water  heating  systems,  however,  the  temperature  of  this 
pipe  would  never  be  less  than  50°,  which  would  cause  an 
expansion  from  hot  to  cold  of  only  .013  inch  per  foot,  or 
1.3  inches  for  each  100  feet  of  straight  pipe.  In  a  steam 
main  the  temperature  may  vary  anywhere  from  50°  to  300°, 
making  a  linear  expansion  of  .02  inch  per  foot  of  length  or  2 
inches  for  each  100  feet  of  straight  pipe.  As  here  shown  the 


DISTRICT   HEATING 


219 


Fi-g.   108. 


movement  from  the  anchor 
at  A  toward  B  may  be  ab- 
sorbed by  the  swinging  of  the 
pipe  about  O.  B.B.  should 
therefore  be  as  long  as  possi- 
ble, say  one  full  block,  to 
avoid  unduly  straining,  the 
pipe  at  the  joints.  Allowing  a 
maximum  movement  of  6 


inches  for  each  expansion  joint,  the  anchors  would  be  spaced 
500  and  300  feet  center  to  center  respectively,  for  hot  water 
and  steam  mains.  These  figures  would  seldom  be  exceeded, 
and  in  some  cases  would  be  reduced,  the  spacing  depending 
upon  the  type  of  expansion  joint  used.  Ordinarily,  400  feet 
spacing  would  be  recommended  for  hot  water  and  300  feet 
for  steam.  If  the  city  layout  meets  this  value  fairly  well, 
then  the  expansion  joints  and  anchors  may  be  made  to 
alternate  with  each  other,  one  each  to  every  city  block. 

A  few  of  the  expansion  joints  in  common  use  are  shown 
in  Jig.  109.  A  is  the  old  slip  and  packed  joint.  This  joint 
causes  very  little  trouble  except  that  it  needs  repacking 
frequently.  It  is  very  effective  when  properly  cared  for. 
The  slip  joint  should  have  bronze  bearings  on  both  the 
outside  of  the  plug  and  the  lining  of  the  sleeve.  The  ends 
of  the  plug  and  sleeve  may  be  screwed  for  small  pipes, 
or  flanged  for  large  ones.  B  shows  an  improved  type  of 
slip  joint,  having  a  roller  bearing  upon  a  plate  in  the 
bottom  of  the  conduit,  and  plugs  bearing  against  metal 
plates  along  the  sides  of  the  conduit  to  keep  it  in  line.  C 
and  D  show  other  slip  joints  very  similar  to  A  and  B.  C 
has  one  ball  and  socket  end  to  adjust  the  joint  to  slight 
changes  in  the  run  of  the  pipe,  and  D  has  two  packings 
enclosing  the  plug  to  give  it  rigidity.  The  drainage  in 
each  case  is  taken  off  at  the  bottom  of  the  casting.  E  has 
two  large  flexible  disks  fastened  to  the  ends  of  the  pipe  and 
separated  from  each  other  by  an  annular  ring  casting. 
These  disks  are  frequently  corrugated,  are  usually  of  cop- 
per and  are  very  large  in  diameter  so  that  the  pipe  has  con- 
siderable movement  without  endangering  the  metal  in  the 
disks.  F  has  a  corrugated  copper  tube  fastened  at  the  ends 
to  the  pipe  flanges.  This  is  protected  from  excessive  inter- 
nal pressure  by  a  straight  tube  having  a  sliding  fit  to  the 
inside  of  the  flanges,  thus  allowing  for  end  movement.  O  is 


220 


HEATING  AND  VENTILATION 


Fig.   109. 


DISTRICT   HEATING 


221 


very  similar  to  E.  It  has,  however,  only  one  copper  disk. 
This  disk  is  enclosed  in  a  cast  iron  casement,  one  side  of 
which  is  iopen  to  the  atmosphere,  the  other  side  having  the 
same  pressure  as  within  the  pipe.  H  is  very  similar  to  E, 
having  two  copper  diaphragms  to  take  up  the  movement. 
These  diaphragms  flex  over  rings  with  curved  edges  and 
are  thus  protected  somewhat  against  failure.  I  shows  a 
copper  U  tube  which  is  sometimes  used.  This  is  set  in  a 
horizontal  position  and  the  expansion  and  contraction  is 
absorbed  by  bending  the  loop.  In  all  these  joints  those 
which  depend  upon  the  bending  of  the  metal  require  little 
attention  except  where  complete  rupture  occurs.  In  old 
plants,  however,  the  rupturing  of  these  diaphragms  is  of 
frequent  occurrence.  The  packed  joint  requires  attention 
for  packing  several  times  in  the  year,  but  very  seldom 
causes  trouble  other  than  this. 

Anchors. — In  any  long  run  of  pipe,  where  the  expansion 
and  contraction  of  the  pipe  causes  it  to  shift  its  position 
very  much,  it  is  necessary  to  anchor  the  pipe  at  intervals  so 
as  to  compel  the  movement  toward  certain  desired  points. 
The  anchor  is  sometimes  combined  with  the  expansion  joint, 
in  which  case  the  conduit  work  is  simplified.  See  Fig.  110. 


Fig.  110. 


222 


HEATING  AND   VENTILATION 


Service  pipes  to  residences  are  taken  off  at  or  near  the, 
anchors.  All  condensation  drains  in  steam  mains  are  like- 
wise taken  off  at  such  points. 

Valves. — All  valves  on  water  systems  should  be  straight- 
way gate  valves.  Valves  on  steam  systems  should  be  gate 
valves  on  lines  carrying  condensation,  and  renewable  seat 
globe  valves  on  the  steam  lines.  Valves  should  be  placed  on 
the  main  trunk  at  the  power  plant,  on  all  the  principal 
branch  mains  as  they  leave  the  main  trunk,  on  all  by-pass 
lines,  on  all  the  service  mains  to  the  houses,  and  at  such 
important  points  along  the  mains  as  will  enable  certain 
portions  of  the  heating  district  to  be  shut  off  for  repairs 
without  cutting  out  the  entire  district. 

Manholes. — Manholes  are  placed  at  important  points  along 
the  line  to  enclose  expansion  joints  and  valves.  These  man- 
holes are  built  of  brick  or  concrete  and  covered  with  iron 
plates,  flag  stones,  slate  or  reinforced  concrete  slabs.  Care 
must  be  exercised  to  drain  these  points  well  and  to  have  the 
covering  strong  enough  to  sustain  the  superimposed  loads. 

140.  Typical  Design  for  Consideration: — In  discussing 
district  heating,  each  important  part  of  the  design  work  will 
be  made  as  general  as  possible  and  will  be  closed  by  an 


1 
RE 

SOENCE 

1 

RESIDE 

NCE 

BUSINESS 
1  1 

kipL 

ANT 

Fig.   111. 


DISTRICT   HEATING 


223 


application  to  the  following  concrete  example  which  refers 
to  a 'certain  portion  of  an  imaginary  city,  Fig.  Ill,  as  avail- 
able territory.  A  city  water  supply  and  lighting"  plant  is 
located  as  shown,  with  lighting  and  power  units  aggregat- 
ing 475  K.  W.,  city  water  supply  pumps  aggregating  3000000 
gallons  maximum  capacity,  and  smaller  units  requiring  ap- 
proximately 15  per  cent,  of  the  amount  of  steam  used  by 
the  larger  lighting  units,  all  as  suggested  in  general  instruc- 
tions in  the  problem  pamphlet.  It  is  desired  to  re-design  this 
plant  and  to  add  a  district  heating  system  to  it;  the  same  to 
have  all  the  latest  methods  of  operation  and  to  be  of  such  a 
size  as  to  be  economically  handled.  Fig.  118  shows  the  essen- 
tial details  of  the  finished  plant. 

141.  Electrical  Output  and  Exhaust  Steam  Available  for 
Heating  Purposes  from  the  Power  Units: — In  the  operation 
of  such  a  plant,  one  of  the  principal  assets  is  the  amount  of 
exhaust  steam  available  for  heating  purposes.  The  amount 
may  be  found  for  any  time  of  the  day  or  night  by  construct- 
ing a  power  chart  as  in  Fig.  112,  and  a  steam  consumption 
chart  as  in  Fig.  113.  Referring  to  Fig.  112,  the  values  here 


500 


400 


200R 


100 


1 

25OK.W  UNIT  

-1C   I/ 

W  UN 
W  UN 

TOTAL 

T  

j 

KW= 

— 

PCWtR  UNIT4)  IN  KW 

-- 

... 

-- 

•m 

•M 

12  I    2  3  4    5  6   7  6  9   10  II    12  I    2  3  4    5  6 
AM  M 

HOURS 
Fig.   112. 


fi  9   10  II    12 
PM 


given  are  assumed,  for  illustration,  to  be  tho.se  recorded  at 
the  switchboard  of  the  typical  plant  on  a  day  when  heavy 
service  is  required.  The  'Curves  show  that  the  75  K.  W.  unit 
runs  from  12  P.  M.  to  7  A.  M.  and  from  6  P.  M.  to  12  P.  M. 
with  an  output  of  25  K,  W.  It  also  runs  from  7  A.  M.  to  10  A. 


224 


HEATING  AND   VENTILATION 


M.  and  from  4  P.  M.  to  6  P.  M.  under  full  load.  The  150  K.  W. 
unit  runs  from  4  A.  M.  to  7  A.  M.  with  an  output  of  100  K.  W. 
and  then 'increases  to  125  K.  W.  for  the  entire  time  until  6  P.  M. 
when  it  is  shut  down.  The  250  K.  TF.  unit  is  started  up  at  7 
A.  M.  and  runs  until  6  P.  M.  under  full  load,  when  the  load 
drops  off  to  150  K.  W.  and  continues  until  10  P.  M.  when  the 
unit  is  shut  dawn,  leaving  only  the  75  K.  W.  unit  running.  The 
heavy  solid  line  shows  all  the  power  curves  superimposed 
one  upon  the  other.  Having1  given  the  A'.  TF.  output,  the  gen- 
eral formula  for  determining  the  horse-power  of  the  engines 
is 

K.  W.  X  1000 

7.   II.  P.  =  -  (66) 

746  X  E  X  E' 

where  E  and  E'  are  the  efficiencies  of  the  generator  and  en- 
gine respectively.  If  we  assume  the  efficiency  of  the  gener- 
ator to  be  90  per  cent.,  and  that  of  the  engine  to  be  92  per 
cent.,  then  formula  66  becomes 

K.  W.  X  1000 

7.  H.  P.  =  —  _  =  approx.  1.62  K.  W.        (67) 

746  X  .90  X  .92 

Assuming  that  the  250  A'.  TF.  unit  consumes  24  pounds,  the 
150  K.  TF.  unit  32  pounds,  and  the  75  K.  TF.  unit  32  pounds  of 
steam  per  I.  H.  P.  hour  respectively,  when  running  under 


?1 

on 

?;« 

in 

PC 

(W 

fli 

W 

Igfi 

^n 

ISfl 

in 

s 

TAM 

~:ON5> 

r 

-M 

Mf\ 

1 

nr 

i4 

sp 

n 

/VM 

-1    1 

M 

5 

KTf 

iSrj 

tf#U 

3  : 

12   I    234    5   6    "7    8    9    10  II    12  1    2    3  4    5   6  "7    8   9    10  II    12 
AM  M  PM 

HOURS 
Fig.   113. 


DISTRICT   HEATING  225 

normal  loads,  we  have  the  total  steam  consumed  in  the  three 
units  at  any  time  shown  by  the  lower  curve  in  Fig.  113. 
The  upper  curve  shows  the  15  per  cent,  added  allowance  for 
smaller  units  not  included  in  the  above  list.  The  values 
assumed  for  efficiencies  and  the  values  for  steam  consump- 
tion are  reasonable,  and  may  be  used  if  a  more  exact 
figure  is  not  to  be  had. 

It  will  be  seen  that  the  maximum  steam  consumption  in 
the  generating  units  in  the  power  plant  is  23100  pounds  per 
hour  and  the  minimum  is  1490  pounds  per  hour.  These  two 
amounts,  then,  together  with  the  exhaust  steam  from  the 
circulating  pumps  on  the  heating  system,  if  a  hot  water 
system  is  installed,  and  that  from  the  pumps  in  the  city 
water  supply,  wiill  determine  ,the  capacity  of  the  exhaust 
steam  heaters  on  the  hot  water  supply  and  the  capacity  of 
the  boilers  or  economizers  to  be  used  as  heaters  when  the 
exhaust  steam  is  deficient. 

142.  Amount  of  Heat  Available  for  Heating  Purposes 
in  Exhaust  Steam,  Compared  with  That  in  Saturated  Steam 
at  the  Pressure  of  the  Exhaust: — To  study  the  effect  of  ex- 
haust steam  upon  heating  problems  and  to  determine,  if 
possible,  the  theoretical  amount  of  heat  given  off  with 
the  exhaust  steam  under  various  conditions  of  use,  let  us 
make  several  applications:  first,  to  a  simple  high  speed 
non-condensing  engine  using  saturated  steam;  second,  to 
a  compound  Corliss  non-condensing  engine  using  saturated 
steam;  third,  to  the  first  application  when  superheated 
steam  is  used  instead  of  saturated  steam;  and  fourth,  to  a 
horizontal  reciprocating  steam  pump.  Assume  the  follow- 
ing safe  conditions.  Case  one — boiler  pressure  100  pounds 
gage;  pressure  of  steam  entering  cylinder  97  pounds  gage; 
quality  of  steam  at  cylinder  98  per  cent.;  steam  consump- 
tion 34  pounds  per  indicated  horse-ipower  hour;  one  per 
cent,  loss  in  radiation  from  cylinder;  and  exhaust  pressure 
2  pounds  gage.  Case  two — boiler  pressure  125  pounds  gage; 
pressure  at  high  pressure  cylinder  122  pounds  gage;  quality 
of  steam  entering  high  pressure  cylinder  98  per  cent.; 
steam  consumption  22  pounds  per  indicated  horse-power 
hour;  2  per  cent,  loss  in  radiation  from  cylinders  and  re- 
ceiver pipe,  and  exhaust  pressure  2  pounds  gage.  Case 
three — same  as  case  one  with  superheated  steam  at  150  de- 
grees of  superheat.  Case  four — as  stated  later. 


226  HEATING   AND   VENTILATION 

The  number  of  B.  t.  u.  exhausted  with  the  steam,  in 
any  case,  is  the  total  heat  in  the  steam  at  admission,  minus 
the  heat  radiated  from  the  cylinder,  minus  the  heat  ab- 
sorbed in  actual  work  in  the  cylinder. 

High  speed  engine.  Case  one. — Let  r  =  heat  of  vaporiza- 
tion per  pound  of  steam  at  the  stated  pressure,  x  =  quality 
of  the  steam  at  cut-off,  q  —  heat  of  the  liquid  in  the 
steam  per  pound  of  steam,  and  W*  =  pounds  of  steam  per 
indicated  horse-power  hour.  From  this  the  total  number 
of  B.  t.  u.  entering  the  cylinder  per  horse-power  hour  is 

Total  B.  t  u.  =  Ws   Or  +  q)  (68) 

From  Peabody's  steam  tables  r  =  881,  x  =  .98  and  q  =  307; 
then  if  Ws  —  34,  initial  B.  t.  u.  =  34  (.98  X  881  +  307)  = 
39792.92.  Deducting  the  heat  radiated  from  the  cylinder 
we  have  39792.92  X  .99  =  39395  B.  t.  u.  per  horse-power 
left  to  do  work.  The  B.  t.  u.  absorbed  in  mechanical  work 
(useful  work  +  friction)  in  the  cylinder  per  horse-power 
hour  is  (33000  X  60)  -r-  778  =  2545  B.  t.  u.  Subtracting 
this  work  loss  we  have  39395  —  2545  =  36850  B.  t.  u.  given 
Uip  to  the  exhaust  per  horse-power  hour.  Comparing  this 
value  with  the  total  heat  in  the  same  weight  of  saturated 
steam  «at  2  pounds  gage,  we  have  100  X  36850  -r-  (34  X 
1152.8)  =  94  per  cent. 

Compound  Corliss  engine.  Case  two. — With  the  same  terms 
as  above  let  r  =  867.4,  SB  =  .98,  q  —  324.4,  and  Ws  =  22, 
then  the  initial  B.  t.  u.  =  22  (.98  X  867.4  +  324.4)  =  25837.9. 
Less  2  per  cent,  radiation  loss  =  25837.9  X  .98  =  25321.14 
B.  t.  u.  The  loss  absorbed  in  doing  mechanical  work  in  the 
cylinder  per  horse-.power  is,  as  before,  2545  B.  it.  u.  Sub- 
tracting this  we  have  25321.14  —  2545  =  22776.14  B.  t.  u. 
given  up  to  the  exhaust  per  horse-power  hour.  Comparing 
as  before  with  saturated  steam  at  2  pounds  gage,  we  have 
100  X  22776.14  -H  (22  X  1152.8)  =  90  per  cent. 

Case  tJiree. — Now  suppose  superheated  steam  be  used  in 
the  first  application,  all  other  conditions  being  the  same, 
the  steam  having  150  degrees  of  superheat,  what  difference 
will  this  make  in  the  result?  The  total  heat  entering  the 
cylinder  .now  is  the  total  heat  of  the  saturated  steam  at 
the  initial  pressure  plus  the  heat  given  to  it  in  the  super- 
heater. Let  Cp  =  specific  heat  of  superheated  steam  and 


DISTRICT   HEATING  227 

ta   =   the    degrees    of   superheat,    then   the   to,tal    heat   of   the 
superheated  steam  is 

Total  B.  t.  u.   (sup.)  =  Ws  (xr  +  q  +  cptd)  (69) 

This  for  one  horse-power  of  steam  (34  pounds),  if  the 
specific  heat  of  superheated  steam  is  .54,  will  be  34  X  .99 
X  (1188  +  .54  X  150)  =  42714.5  B.  t.  u.  and  the  heat  turned 
into  the  exhaust  will  be  42714.5  —  2545  =  40169.5  B.  t.  u. 
Comparing-  this  with  the  heat  in  saturated  steam  at  2 
pounds  gage,  we  have  100  X  40169.5  -h  (34  X  1152.8)  =  102 
per  cent. 

Case  four. — Pump  exhausts  are  sometimes  led  into  the 
supply  and  used  for  heating  purposes  along  with  the  engine 
exhausts.  If  such  conditions  be  found,  what  is  the  heating 
value  of  such  steam?  Assume  the  live  steam  to  enter  the 
steam  cylinder  of  the  pump  under  the  same  pressure  and 
quality  as  recorded  for  the  high  speed  engine.  The  steam 
is  cut  off  at  about  %  of  the  stroke  and  expands  to  the  end 
of  the  stroke.  With  this  small  expansion  the  absolute 
pressure  at  the  end  of  the  stroke  will  be  approximately 
%  X  112  =  98  pounds,  and  if  enough  heat  is  absorbed  from 
the  cylinder  wall  to  bring  the  steam  up  to  saturation  at 
the  release  pressure,  we  will  have  a  total  heat  above  32 
degrees,  in  the  exhaust  steam  per  pound  of  steam  at  98 
pounds  absolute,  of  1185.6  B.  -t.  u.  Comparing  this  with  a 
pound  of  saturated  steam  at  2  pounds  gage,  we  have 
100  X  1185.6  -i-  1152.8  =  103  per  cent.  Under  the  con- 
ditions such  as  here  stated  with  a  high  release  pressure, 
a  small  expansion  of  steam  in  the  cylinder  and  dry  steam 
at  the  end  of  the  stroke,  it  is  possible  to  suddenly  drop  the 
pressure  from  pump  release  to  a  low  pressure,  say  2  pounds 
gage,  and  have  all  the  steam  brought  to  a  state  approach- 
ing .superheat.  It  is  not  likely,  however,  that  the  steam 
is  dry  at  the  end  of  the  stroke  in  any  pump  exhaust,  be- 
cause the  heat  lost  in  radiation  and  in  doing  work  in  the 
slow  moving  pump  would  be  such  as  to  have  a  considerable 
amount  of  entrained  water  with  the  steam,  thus  lowering 
the  quaMty  of  the  steam.  These  above  conditions  are  ex- 
treme and  are  not  obtained  in  practice. 

From  cases  one  and.  two  it  would  appear  that  the 
greatest  amount  of  heat  that  can  be  expected  from  engine 
exhausts,  for  use  in  heating  systems  at  or  near  the  pres- 
sure of  the  atmosphere,  is  90  to  94  per  cent,  of  that  of 


228 


HEATING   AND   VENTILATION 


saturated  steam  at  the  same  pressure.  The  percentage  will, 
in  most  cases,  drop  much  below  this  value.  All  things  con- 
sidered, exhaust  steam  having  80  to  85  per  cent,  of  the  value  of 
saturated  steam  at  the  same  pressure  is  probably  the  safest  rating  when 
calculating  the  amount  of  radiation  which  can  be  supplied  by  the 
engines.  In  many  cases  no  doubt  this  could  be  exceeded,  but 
it  is  always  best  to  take  a  safe  value.  On  the  other  hand, 
when  figuring  the  amount  of  condenser  tube  surface  or  reheater  tube 
surface  to  condense  the  steam,  it  would  be  best  to  take  exhaust  steam 
at  100  per  cent,  quality,  since  this  would  be  working  toward 
the  side  of  safety. 

In  plants  where  the  exhaust  steam  is  used  for  heating 
purposes  and  where  the  amount  supplied  by  direct  acting 
steam  pumps  is  large  compared  with  that  supplied  by  the 
power  units,  it  is  possible  to  have  the  quality  of  the  ex- 
hausts anywhere  between  800  and  1000  B.  t.  u.  per  pound 
of  exhaust.  It  should  be  understood  that  saturated  steam 
at  any  stated  pressure  always  has  the  isame  number  of 
B.  .t.  u.  in  it,  no  matter  whether  it  is  taken  directly  from 
the  boiler,  or  from  the  engine  exhaust.  A  pound  of  the 
mixture  of  steam  and  entrained  water,  taken  from  engine 
exhausts,  should  not  be  considered  as  a  pound  of  steam. 
If  we  are  speaking  of  a  pound  of  exhaust  steam  without 
the  entrained  water  as  compared  with  a  pound  of  saturated 
steam  at  the  same  pressure,  they  <are  the  same,  but  a  pound 
of  engine  exhaust  or  mixture  is  a  different  thing. 


Fig.   114. 


DISTRICT    HEATING 


229 


HOT    WATER   SYSTEMS. 

143.  Pour  General  Classifications  of  hot  water  heating 
may  be  found  in  current  work,  two  applying  to  the  conduit 
piping  system  and  tW'O  to  the  power  plant  piping  system. 
The  first,  known  as  the  one-pipe  complete  circuit  system,  is  shown 
in  Fig.  114.  It  will  be  noticed  that  the  water  leaves  the 
power  plant  and  makes  a  complete  circuit  of  the  district, 
as  A,  B,  C,  D,  E,  F,  O,  through  a  single  pipe  of  uniform 
diameter.  From  this  main  are  taken  branch  mains  and 
leads  to  the  various  houses,  as  a,  6,  c  and  d,  e,  each  one 
returning  to  the  principal  main  after  having  made  its  own 
minor  circuit.  The  second  is  known  as  the  two-pipe  high 
pressure  system,  in  which  two  main  pipes  of  like  diameter 
laid  side  by  side  in  the  same  conduit,  radiate  from  the 
power  plant  to  the  farthest  point  on  the  line  reducing 
in  size  at  certain  points  to  suit  the  capacity  of  that  part 
of  the  district  served.  This  system  is  represented  by  Fig. 
115.  In  the  one-pipe  system  the  circulation  in  the  various 
residences  is  maintained,  in  part,  by  what  is  known  as  the 
shunt  system^  and  in  part,  by  the  natural  gravity  circula- 
tion. The  circulation  in  the  two-pipe  system  is  main- 
tained by  a  high  differential  pressure  between  the  main 
and  the  return  at  the  same  point  of  the  conduit.  The  force 
producing  movement  of  the  water  in  the  shunt  system  is, 
therefore,  very  much  less  than  in  the  two-pipe  system.  As  a 
consequence,  the  one-pipe  system  has  a  lower  velocity  of  the 


Fij.  115. 


POWER  Hou&t 


230  HEATING  AND  VENTILATION 

water  in  the  houses  and  larger  service  pipes  than  the  two- 
pipe  system. 

In  many  cases  it  is  desired  to  connect  central  heating 
mains  to  the  low  pressure  hot  water  systems  in  private 
plants.  Such  connections  may  easily  be  made  with  either 
one  of  the  two  systems  by  installing  some  minor  pieces 
of  apparatus  for  controlling  the  supply. 

The  third  and  fourth  classifications,  the  open  and  closed 
systems,  have  about  the  same  meaning  as  when  applied  to 
gravity  work  in  isolated  plants.  The  first  is  open  to  the 
atmosphere  at  some  point  along  the  circulating  system,  usu- 
ally at  the  expansion  tank  which  is  placed  on  the  return 
line  just  before  the  circulating  pumps.  The  closed  system 
presupposes  some  form  of  regulation  for  controlling  exces- 
sive or  deficient  pressures  without  the  aid  of  an  expansion 
tank.  In  such  cases  pumps  with  automatic  control  may  be 
used  for  taking  care  of  the  reserve  supply  of  water.  In  the 
open  system  the  exhaust  steam  may  be  injected  directly  into 
the  return  circulating  water  by  the  use  of  an  open  heater 
or  a  com-mingler.  The  open  heater  and  com-mingler  cannot 
be  used  on  the  pressure  side  of  the  pumps.  Surface  con- 
densers or  reheaters,  heating  boilers  and  economizers  may 
be  used  on  either  open  or  closed  systems. 

144.  Amount  of  Water  Needed  per  Hour  as  a  Heating 
Medium:— All  calculations  must  necessarily  begin  with  the 
heat  lost  at  the  residence.  Referring  to  the  standard  room 
mentioned  in  Art.  80,  we  find  the  heat  loss  to  be  14000  B.  t.  u. 
per  hour,  requiring  84  square  feet  of  hot  water  heating  sur- 
face to  heat  the  room.  Let  the  circulating  water  have  the 
following  temperatures:  leaving  the  power  plant  180°,  enter- 
ing the  radiator  177°,  leaving  the  radiator  157°,  and  entering 
the  power  plant  155°.  According  to  these  figures,  which  may 
be  considered  fair  average  values,  the  water  gives  off  to  the 
radiator  20  B.  t.  u.  per  pound  or  166.6  B.  t.  u.  per  gallon,  thus 
requiring  14000  4-  166.6  =  84  gallons  of  water  per  hour  to 
maintain  the  room  at  a  temperature  of  70°.  From  this  a 
safe  estimate  may  be  given  for  design,  i.  e.,  each  square  foot  of 
hot  water  radiation  in  the  city  will  require  approximately  one  gallon 
of  water  per  hour,  which  in  a  plant  operating  under  high  effi- 
ciency may  be  reduced  to  6  pounds  per  square  foot  per  hour. 
It  is  very  certain  that  some  plants  are  designed  to  supply 
less  than  one  gallon,  but  in  such  cases  it  requires  a  higher 
temperature  of  the  circulating  water  and  allows  little  chance 


DISTRICT   HEATING  231 

for  future  expansion  of  the  plant.  A  drop  of  20  degrees, 
i.  e.,  20  B.  t.  u.  heat  loss  per  pound  of  water  passdng  through 
the  radiator,  is  probably  the  most  satisfactory  basis.  All 
things  considered,  the  above  italicised  statement  will  satisfy 
every  condition.  (See  Art.  173).  Having  the  total  number 
of  square  feet  of  radiation  in  the  district,  the  total  amount 
of  water  circulated  through  the  mains  per  hour  can  be 
obtained,  after  which  the  size  of  the  pumps  in  the  power 
plant  may  be  estimated. 

145.  Radiation  in  the   District: — The   amount   of   radia- 
tion that  may  be  installed  in  the  district  is  problematical.    In 
an  average  residence  or  business  district  the  following  fig- 
ures  may   easily   be   realized:    business   square,   9000  square   feet; 
residence  square,  4500  square  feet.     In  certain  locations  these  fig- 
ures may  be  exceeded  and   in   others  they  may  be   reduced. 
Where  the  needs  of  the  district  are  thoroughly  understood  a 
more  careful  estimate  can  easily  be  made.     It  is  always  well 
to  make  the  first  estimate  a  safe  one  and  any  possible  in- 
crease above   this   figure   could  be   taken   care   of  as    in  Art. 
144.     Referring   to   Fig.    Ill,   an   estimate  of   the  amount   of 
radiation  that  may  be   expected  in  this  typical   case,  if  we 
assume     ten     business     squares    and     twenty-one     residence 
squares,  is  184500  square  feet.     This  will  call  for  the  circu- 
lation of  184500  gallons   of  water  per  hour. 

146.  Future  Increase  in  Radiation: — From  the  tempera- 
tures given  in  Art.   144,   it  will  be  seen  that  each   pound  of 
water  takes  on  25  B.  t.  u.  at  the  power  plant  and  that  there 
is  a  possible  increase  of  212  —  180  =  32  B.  t.  u.  per  pound  that 
may  be  given  to  it,  thus  increasing  the  capacity  of  the  system 
approximately  125  per  cent.     It  would  not  be  safe  to  count 
on  such  an  increase  in  the  average  plant  because  of  a  defec- 
tive layout  in   the   piping  system  or  because   of  a  low   effi- 
ciency   in    some    of    the    pumps    or    other    apparatus    in    the 
plant.      If,    however,    a    plant    is    installed   according    to    the 
above  figures,  the  capacity  may  be  quite  materially  increased 
by  increasing  the  temperature  of  the  outgoing  water 'at  th« 
plant  to  212°. 

147.  The  Pressure  of  the  Water  in  the  Mains: — The  ele- 
vation above  the  plant  at  which  a  central  station  can  supply 
radiation  is  limited.     Water  at  180°  will  weigh  60.55  pounds 
per  cubic  foot,  and  the  pressure  caused  by  an  elevation  of  1 
foot  is  .42  pound  per  square  inch.     From  this  the  static  pres- 


232  HEATING  AND   VENTILATION 

sure  at  the  power  plant,  due  to  a  hydraulic  head  of  100  feet, 
is  42  pounds  per  square  inch.  This  value  should  not  be  ex- 
ceeded, and  generally,  because  of  the  influence  it  has  on  the 
machines  and  pipes  toward  producing  leaks  or  complete 
ruptures,  a  less  head  than  this  is  desirable.  A  static  pres- 
sure of  42  pounds  may  be  expected  to  produce,  in  a  well  de- 
signed plant,  an  outflow  pressure  of  G5  to  75  pounds  per 
square  inch  and  a  return  pressure  of  15  to  20  pounds  per 
square  inch,  when  working  under  fairly  heavy  service.  In 
any  case  where  the  mains  are  too  small  to  supply  the  radia- 
tion in  the  system  properly,  we  may  expect  the  value  given 
for  the  outflow  to  increase  and  that  for  the  return  to  de- 
crease. A  safe  set  of  conditions  to  follow  is:  head,  in  feet, 
60;  static  pressure,  in  pounds  per  square  inch,  25;  outgoing 
pressure  at  the  pumps,  in  pounds  per  square  inch,  50;  return 
pressure  at  the  pumps,  in  pounds  per  square  inch,  5. 
This  differential  pressure  of  45  pounds  is  caused  by  the 
friction  losses  in  the  piping  system,  pumps  and  heaters. 
Long  pipe  systems,  as  these  are  called,  have  much  greater 
friction  losses  in  the  long  runs  of  piping  than  in  the  ells, 
tees,  valves,  etc.,  hence,  the  friction  head  of  the  pipes  is  all 
that  is  usually  considered.  Where  the  minor  losses  are 
thought  to  be  large,  they  may  be  accounted  for  by  adding 
to  the  pipe  loss  a  certain  percentage  of  itself,  say  10  to  20 
per  cent.  Pump  power  is  figured  from  the  differential  pressure. 

The  maximum  and  minimum  pressures  in  the  system  are 
due  to  two  causes;  first,  the  static  head,  and  second,  the 
frictional  resistances.  These  extremes  of  pressure  are  ap- 
proximately— static  head  plus  (or  minus)  one-half  the  frictional 
resistances.  To  obtain  the  frictional  resistances,  Chezy's  for- 
mula, 70,  is  recommended.  See  Merriman's  "A  Treatise 
on  Hydraulics,"  Arts.  86  and  100,  and  Church's  "Mechanics 
of  Engineering,"  Art.  519. 

4<6 1        vz 

hf=-—X—  (70) 

d          2g 

where  hf  =  feet  of  head  lost  in  friction,  <f>  =  friction  factor 
(synonymous  with  coefficient  of  friction.  For  clean  cast 
iron  pipes  with  a  velocity  of  5  to  6  feet  per  second  this 
has  been  found  to  vary  from  .0065  to  .0048  for  diameters 
between  3  and  15  inches  respectively.  .005  is  suggested  as 
a  safe  average  value  to  use),  I  =  length  of  pipe  in  feet, 
v  =  velocity  of  water  in  feet  per  second,  d  =  diameter 
of  pipe  in  feet  and  2g  =  64.4. 


DISTRICT   HEATING  233 

APPLICATION.  —  In  Fig.  115,  let  it  be  desired  to  find  the 
differential  pressure  at  the  pumps  due  to  the  friction  losses 
in  the  line  A,  B,  C,  D,  E.  The  lengths  of  'the  various  parts 
are:  power  plant  to  A,  200  feet;  A  to  B,  500  feet;  B  to  C, 
1500  feet;  C  to  D,  1500  feet;  and  D  to  E,  500  feet.  Assume, 
for  illustration,  that  the  total  radiation  in  square  feet 
beyond  each  of  these  points  is:  power  plant,  125000;  A,  85000; 
B,  50000;  C,  28000;  and  D,  12000.  This  requires  125000,  85000, 
50000,  28000  and  12000  '  gallons  of  water  per  hour,  or  4.74, 
3.27,  1.75,  1  and  .44  cubic  feet  of  water  per  second,  respec- 
tively, passing  these  points.  Now,  .  if  the  velocities  be 
roughly  taken  at  6  and  5  feet  per  second,  (pipes  near  the 
power  plant  may  be  given  somewhat  higher  velocities  than 
those  at  some  distance  from  the  plant),  the  pipes  will  be  12, 
10,  8,  6  and  4  inches  diameter.  In  applying  the  formula  to 
one  part  of  the  line  we  show  the  method  employed  for  each. 
Take  that  part  from  the  power  plant  to  A.  With  v  =  6 

4   X  .005   X   200   X   36 

=  2.2  feet. 


64.4   X   1 

It  should  be  noted  here  that  formula  70  refers  to  pipes 
where  all  the  water  that  enters  at  one  end  passes  out  the  other. 
This  is  not  true  in  heating  mains  where  a  part  of  the  water 
is  drawn  off  at  intermediate  points.  On  the  other  hand, 
Merriman,  Art.  99,  explains  that  a  water  service  main,  where 
the  water  is  all  taken  off  from  intermediate  tappings  and  where 
the  velocity  at  the  far  qnd  is  zero,  causes  only  one-third  of  the 
friction  given  by  the  above  formula.  The  case  under  consid- 
eration falls  somewhere  between  these  two  extremes,  the  part 
next  the  power  plant  approaching  the  former  and  the  last 
part  of  the  line  exactly  meeting  the  conditions  of  the  latter. 
Assuming  the  mean  of  'these  two  conditions,  which  is 
probably  very  close  to  the  actual,  gives  two-thirds  of  'that 
found  by  the  formula.  Now  since  this  is  a  double  main 
system,  i.  e.,  main  and  return  of  the  .same  size,  the  friction 
head  for  the  two  lines  becomes  2.94  feet,  from  the  power 
plant  to  A.  In  a  similar  way  the  other  parts  may  be  tried 
and  the  results  from  the  entire  line  assembled  in  convenient 
form  as  in  Table  XXVII. 


234 


HEATING  AND   VENTILATION 


TABLE  XXVII. 


P.  P. 
to  A. 

AtoB 

Bto  C 

CtoD 

DtoE 

Distance  between  points  

Radiation    supplied 

200 

125000 

500 
85000 

1500 
50000 

1500 

^9000 

503 

Volume  of  water  passing 
point   in   cu.    ft.    per   sec  
Velocity   f.    p.    s  

4.74 
g 

3.27 
g 

1.75 
5 

1. 

5 

.44 
5 

Area  of  pipe  sq.  ft  

79 

545 

35 

9Q 

087 

Diam.   of  pipe  in  ft  

1 

83 

66 

5 

33 

hf  by   (73)    for  flow  main 

2  2 

67 

17  4 

23  3 

11  7 

hf    (taking   %   value)      

1  47 

4  47 

11  6 

15  5 

7  8 

hf   (%  val.  flow  and  return).... 

2.94 

8.94 

23.2 

31.0 

15.6 

From  the  last  line  of  the  table  we  obtain  the  total 
friction  head  for  both  mains,  not  including  ells,  tees,  valves, 
etc.,  to  be  81.6  feet.  This  is  equivalent  to  34.3  pounds  per 
square  (inch.  Now  if  we  allow  about  20  per  cent,  of  all  the 
line  losses  to  cover  the  minor  losses  we  have  approximately 
40  pounds  differential  pressure,  which  is  a  reasonable  value. 

148.  Velocity  of  the  Water  in  the  Mains  and  the  Dia- 
meter of  the  Mains: — The  district  is  first  chosen  and  the 
layout  of  the  conduit  system  is  made.  This  is  done  inde- 
pendently of  the  sizes  of  the  pipes.  When  this  layout  is 
finally  completed,  the  pipe  sizes  are  roughly  calculated  for 
all  the  important  points  in  the  system  and  are  tabulated 
in  connection  with  the  friction  losses  for  these  parts,  as 
in  Art.  147.  When  this  is  done,  formula  71,  which  is  rec- 
ommended to  be  used  in  connection  with  formula  70,  may  be 
applied  and  the  'theoretical  diameters  found.  (The  approxi- 
mate diameters  and  the  friction  heads  need  not  be  calcu- 
lated in  formula  70  for  use  in  formula  71,  providing  some 
estimate  may  be  made  for  the  value  of  hf,  for  the  various 
lengths  of  pipe.  If  desired,  hf  may  be  assumed  without  any 
reference  to  the  diameter,  but  this  is  a  rather  tedious  pro- 
cess. For  good  discussion  of  this  point  see  Church's  Hy- 
draulic Motors,  Arts.  121-124  b.) 


%  X 


<t>1Q2 


(71) 


where  d,  hf,  $  and  I  are  the  same  as  in  formula  70,  and  0  == 
cubic  feet  of  water  passing  through  the  pipe  per  second. 
This  formula  differs  from  those  given  in  the  references 
stated,  in  that  the  term  %  is  inserted  as  a  mean  value  be- 


DISTRICT   HEATING  235 

tween    the    two    extreme    conditions,    as    stated    in   Art.    147. 
APPLICATION.  —  Let  it  be  desired  to  find  the  diameter  for  the 
single  main  between  the  power  plant  and  A,  Art.   147,  with 
hf  =  1.47 


2  X.005  X  200  X  (4.74)2 
3   X   1.47 


15/5 

I     =  1  ft.  =  12  in. 
J 


Applying  to  the  entire  line  with  hf  as  given  in  next  to  last 
line  of  Table  XXVII,  gives  power  plant  to  A,  d  =  12  inches; 
A  to  B,  d  =  10  inches;  B  to  C,  d  =  8  inches;  C  to  D,  d  =  6 
inches;  and  D  to  E,  d  =  4  inches. 

In  some  cases,  when  close  estimating  is  not  required, 
it  is  satisfactory  to  assume  a  velocity  of  the  water  and  find 
the  diameter  without  considering  the  friction  loss.  In  many 
cases,  however,  this  would  soon  prove  a  positive  loss  to  the 
company.  With  a  low  velocity,  the  first  cost  would  be  large 
and  the  operating  cost  would  be  low.  On  the  other  hand, 
if  the  velocity  were  high,  the  first  cost  would  be  small  and 
the  operating  cost  and  depreciation  would  be  large.  As  an 
illustration  of  how  the  friction  head  increases  in  a  pipe  of 
this  kind  with  increased  velocity,  refer  to  the  run  of  mains 
between  B  and  C.  Assuming  a  velocity  of  10  feet  per 
second,  which  in  this  case  would  be  very  high,  the  friction 
head,  hf,  for  the  single  main,  becomes  62  and  the  theoretical 
diameter  is  5.5,  say  6  inches.  The  friction  head,  as  will  be 
seen,  is  5.4  times  the  corresponding  value  when  the  velocity 
was  5  feet  per  second.  Since  the  pump  must  work  contin- 
ually against  this  head,  it  would  incur  a  financial  loss  that 
would  soon  exceed  the  extra  cost  of  installing  larger  pipes. 
It  is  found  in  plants  that  are  in  first  class  operation  that 
the  velocities  range  from  5  to  7  feet  per  second. 

The  calculations  in  Arts.  147  and  148  are  very  much 
simplified  by  the  use  of  the  chart  shown  in  the  Appendix. 
In  planning  a  system  of  this  kind,  find  the  friction  head 
on  the  pumps  and  the  diameters  of  the  pipes  for  various 
velocities,  say  4,  6,  8  and  10  feet  per  second.  Estimate  the 
probable  first  cost  and  the  depreciatioi?  of  the  conduit  sys- 
tem for  each  velocity,  and  balance  these  figures  with  the 
operating  cost  for  a  period  of,  say  five  years,  to  see  which  is 
the  most  economical  velocity  to  use  in  figuring  the  system. 

149.  Service  Connections  are  usually  installed  from  30 
to  36  inches  below  the  surface  of  the  ground,  and  are  in- 
sulated in  some  form  of  box  conduit  which  compares  favor- 


236  HEATING  AND   VENTILATION 

ably  with  that  of  the  main  conduit.  Service  branches  are 
l1^,  1^  and  2  inch  wrought  iron  pipe.  These  are  usually 
carried  to  the  building  from  the  conduit  at  the  expense  of 
the  consumer.  Such  branch  conduits  ar,e  not  drained  by 
tile  drains.  See  Art.  176. 

15O.  Total  Steam  Available  and  B.  t.  u.  Liberated  per 
Hour  for  Heating  the  Circulating  AVater: — The  amount  of 
steam  available  for  heating  the  circulating  water  is  that 
given  off  by  the  generating  units,  plus  that  from  the  cir- 
culating pumps,  plus  that  from  the  city  water  supply  pumps 
if  there  be  any,  plus  that  from  the  auxiliary  steam  units 
in  the  plant,  i.  e.,  small  pumps,  engines,  etc.  In  the  typical 
application  this  amounts  to  23100  +  12720  +  8680  =  44500 
pounds  per  hour. 

This  steam,  of  course,  is  not  equal  to  good  dry  steam  in 
heating  value  because  of  the  work  it  has  done  in  the  engine 
and  pump  cylinders,  but  a  good  estimate  of  its  value  may 
be  approximated.  In  addition  to  the  terms  used  in  for- 
mula 68,  let  q'  =  heat  in  the  returning  condensation  per 
pound;  then  the  heat  available  for  heating  purposes  per 
pound  of  exhaust  steam  is 

B.  t.  u.  =  xr  +  q  —  q'  (72) 

It  is  probably  safe  to  consider  the  quality  of  the  steam  as 
85  per  cent,  of  that  of  good  dry  steam  at  the  same  pressure. 
Since  the  pressure  of  the  exhaust  from  a  non-condensing 
engine,  as  it  enters  the  heater,  is  near  that  of  the  atmos- 
phere, and  since  the  returning  condensation  is  at  a  tempera- 
ture of  about  180°,  the  total  amount  of  heat  given  off  from 
a  pound  of  exhaust  steam  to  the  circulating  water  is 
B.  t.  u.  =  .85  X  969.7  +  180.3  —  (180.3  —  32)  —  856,  say  850. 
If  Ws  be  the  pounds  of  exhaust  steam  available,  the  total 
number  of  B.  t.  u.  given  off  from  the  exhaust  steam  per  hour  is 

Total  B.  t  u.  =  850  W*  (73) 

Applying  this  to  the  typical  power  plant  gives  850  X 
44500  =  37825000  B.  t.  u.  per  hour.  This  amount  is  probably 
a  maximum  under  the  conditions  of  lighting  units  as  stated, 
and  would  be  true  for  only  5  hours  out  of  24.  At  other 
times  the  exhausi;  steam  drops  off  from  the  lighting  units 
and  this  deficiency  must  be  made  good  by  heating  the  circu- 
lating water  directly  from  the  coal,  by  passing  the  water 
through  heating  boilers  or  by  passing  it  through  economiz- 


DISTRICT   HEATING  237 

ers   where    it   is    heated    by   the    waste   heat   from    the   stack 
gases. 

151.  Amount    of    Hot    Water    Radiation    In    the    District 
that  can  be  Supplied  by  One  Pound  of  Exhaust  Steam  on  a 
Zero   Day:  —  In   Art.    144,    each   pound   of   water   takes   on    25 
B.  t.  u.  in  passing  through  the  reheaters  at  the  power  plant, 
and   gives    off   at   least    20    B.    t.    u.    in    passing   through    the 
radiator.     The  number  of  pounds  of  water  heated  per  pound 
of   steam   per   hour   is,    Ww   =    (Total   B.   t.    u.    available   per 
pound  of  exhaust  steam  per  hour)  -T-  25,  and  the  total  radia- 
tion that  can  be  supplied  is 

Total  B.  t  u.  available  per  Ib.  of  exhaust  steam  per  hr. 
Rw  =  --  -   (74) 

8.33   X   25 

which  for  average  practice  reduces  to 

850 
Rw  =  -  =  4  square  feet  approx.  (75) 

208 

Applying  formula  74  for  the  five  hour  period  when  the 
exhaust  steam  is  maximum  gives  Rw  =  37825000  -T-  20'8  = 
181851  square  feet.  It  is  not  safe  to  figure  on  the  peak  load 
conditions.  It  is  better  to  assume  that  for  half  the  time, 
35000  pounds  of  steam  are  available  and  will  heat  35000 
X  4  =  140000  square  feet  of  radiation. 

152.  The  Amount  of  Circulating  "Water  Passed  through 
the    Heater    Necessary   to    Condense    One    Pound    of    Exhaust 
Steam  is 

Total  B.  t.  u.  available  per  Ib.  of  exhaust  steam  per  hr. 


25 


(76) 


With    the    value    given    above    for    the    exhaust    steam    this 
becomes,   for   100  and   85    per  cent,    respectively, 

1000 

Ww  =  -  =  40  pounds  (77) 

25 

850 

Ww  =  -  =  34  pounds  (78) 

25 

153.  Amount  of  Hot  Water  Radiation  in  the  District 
that  can  be  Heated  by  One  Horse-Power  of  Exhaust  Steam 
from  a  Non-Condensing  Engine  on  a  Zero  Day:  — 

Rw  =  4  X   (pounds  of  steam  per  H.  P.  hour)          (79) 


238  HEATING   AND  VENTILATION 

This  reduces  for  the  various  types  of  engines,  as  follows: 

Simple    high    speed  4   X   34  =  136  square  feet. 

medium  "  4  X  30  =  120 

Corliss  4  X  26  =  104 

Compound  high  "  4  X  26  =  104          "         * 

"      medium"  4  X  25  =  100 

"      Corliss  4  X   22  =     88 

154.  Amount  of  Radiation  that  can  be  Supplied  by  Ex- 
haust   Steam   in   Formulas   74   and   75   at   any  other   Temper- 
ature   of    the    Water,    /,.-,    than    that    Stated,    with    the    Room 
Temperature,  t',  Remaining  the  Same: — The  amount  of  heat 
passing  through  one  square  foot  of  the  radiator  to  the  room 
is  in  proportion  to  tw  —  f.     In  formulas  74  and  75,  tw  —  tr  = 
100.     Now   if  tw   be   increased  a?  degrees,   so   that  tw  —  t'  = 
(100  +  x)  then  each  square  foot  of  radiation  in  the  building 

100  +  x 

will    give    off    times    more    heat    than    before    and 

100 

each  pound  of  exhaust  steam  will  supply  only 

4  X  100 

Rw  = square  feet  (80) 

100  +  a? 

This  for  an  increase  of  30  degrees,  which  is  probably  a  max- 
imum, is 

4 
7J»  =  =  3  square  feet  (81) 

Compared  with  formula  75,  formula  80  shows,  with  a  higu 
temperature  of  the  water  entering  the  radiator,  that  less 
radiation  is  necessary  to  heat  any  one  room  and  that  each 
square  foot  of  surface  becomes  more  nearly  the  value  of  an 
equal  amount  of  steam  heating  surface.  Calculations  for 
radiation,  however,  are  seldom  made  from  high  tempera- 
tures of  the  water,  and  this  article  should  be  considered  an 
exceptional  case. 

155.  Exhaust  Steam  Condenser  (Reheater),  for  Reheat- 
ing   the    Circulating    Water: — In    the    layout    of    any    plant 
the    reheaters    should    be    located    close    to    the    circulating 
pumps    on    the    high    pressure    side.      They    are    usually    of 
the  surface  condenser  type,  Fig.  116,  and  may  or  may  not  be 
installed  in  duplicate.     Of  the  two  types  shown   in  the  fig- 
ure, the  water  tube  type  is  probably  the  more  common.     The 
same  principles  hold  for  each  in  design.     In  ordinary  heaters 
for  feed  water  service,  wrought  iron  tubes  of  1^    to  2  inches 


DISTRICT   HEATING 


239 


WATER 


I  DRIP 


WATLR-TUBt  TYPE 


MLR      STCAM 
DRIP 


Fig-.  116. 


STLAM-TUBt  TYPE 


diameter  are  generally  used,  but  for  condenser  work  and 
where  a  rapid  heat  transmission  is  desired,  brass  or  copper 
tubes  are  used,  having  diameters  of  %  to  1  inch.  In  heating 
the  circulating  water  for  'district  service,  the  ireheater  is 
doing1  very  much  the  same  work  as  if  used  on  the  condens- 
ing system  for  engines  or  turbines.  The  chief  difference  is 
in  the  pressures  carried  on  the  steam  side,  the  reheater  con- 
densing- the  steam  near  atmospheric  pressure  and  the  con- 
denser carrying  about  .9  of  a  perfect  vacuum.  In  either  case 
it  should  be  piped  on  the  water  side  for  water  inlet  and  out- 
let, while  the  steam  side  should  be  connected  to  the  exhaust 
line  from  the  engines  and  pumps,  and  should  have  proper 
drip  connection  to  draw  the  water  of  condensation  off  to  a 
condenser  pump.  This  condenser  pump  usually  delivers  the 
water  of  condensation  to  a  storage  tank  for  use  as  boiler 
feed,  or  for  use  in  making  up  the  supply  in  the  heating  sys- 
tem. 

In  determining-  the  details  of  the  condenser  the  following 
important  points  should  be  investigated:  the  amount  of 
heating  surface  in  the  tubes,  the  size  of  the  water  inlet  and 
outlet,  the  size  of  the  pipe  for  the  steam  connection,  the  size 
of  the  pipe  for  the  water  of  condensation  and  the  length 
and  cross  section  of  the  heater. 

156.  Amount  of  Heating  Surface  In  the  Reheater  Tubest 
— The  general  formula  for  calculating  the  heating  surface  in 
the  tubes  of  a  reheater  (assuming  all  heating  surface  on 
tubes  only),  is 

Total  B.  t.  u.  given  up  by  the  exhaust  .steam  per  hr. 

Rt  =  (82) 

K  (Temp.  diff.  between  inside  and  outside  of  tubes) 

The  maximum  heat  given  off  from  one  pound  of  exhaust 
steam  in  condensing  at  atmospheric  pressure  is  1000  B.  t.  u., 
the  average  temperature  difference  is  approximately  47 
degrees,  and  K  may  be  taken  427  B.  t.  u.  per  degree  dif- 


240  HEATING  AND  VENTILATION 

ference  per  hour.  In  determining  K,  it  is  not  an  easy  mat- 
ter to  obtain  a  value  that  will  be  true  for  average  practice. 
Carpenter's  H.  &  V.  B.  Art.  47  quotes  the  above  figure  for 
tests  upon  clean  tubes,  and  volumes  of  water  less  than 
1000  pounds  per  square  foot  of  heating  surface  per  hour. 
It  is  found,  however,  that  the  average  heater  or  condenser 
tube  with  its  lime  and  mud  deposit  will  reduce  the  efficiency 
as  low  as  40  to  50  per  cent,  of  the  maximum  transmission. 
Assume  this  value  to  be  45  per  cent.;  then  if  Ws  is  the 
number  of  pounds  available  exhaust  steam,  formula  82 
becomes 

1000  Ws  1000  Ws  1000  Ws          Ws 

Rt  = = = = (83) 

K  (ts—tw)          427  X  .45  X  47  9031  9.1 

In  "Steam  Engine  Design,"  by  Whitham,  page  283,  the 
following  formula  is  given  for  surface  condensers  used  on 
shipboard: 

W  L 

S  = 

CK  (Tx  -  *) 

where  8  =  tube  surface,  W  •=.  total  pounds  of  exhaust  steam 
to  be  condensed  per  hour,  L  =  latent  heat  of  saturated  steam 
at  a  temperature  Tit  K  =  theoretical  transmission  of  B.  t.  u. 
per  hour  through  one  square  foot  of  surface  per  degree  dif- 
ference of  temperature  =  556.8  for  brass,  c  =  efficiency  of 
the  condensing  surface  =  .323  (quoted  from  Isherwood),  TI  = 
temperature  of  saturated  steam  in  the  condensers,  and  t  = 
average  temperature  of  the  circulating  water. 

With  L  =  969.7,  c  =  .323,  K  =  556.8  and  TI  —  t  =  47,  we 
may  state  the  formula  in  terms  of  our  text  as 

969.7  W,  969.7  Ws          Ws 

Rt  =  =  =  (84) 

.323X556.8X47  8446  8.7 

In  Sutcliffe  "Steam  Power  and  Mill  Work,"  page  512,  the 
author  states  that  condenser  tubes  in  good  condition  and  set 
in  the  ordinary  way  have  a  condensing  power  equivalent  to 
13000  B.  t.  u.  per  square  foot  per  hour,  when  the  condensing 
water  is  supplied  at  60  degrees  and  rises  to  95  degrees  at  dis- 
charge, although  the  author  gives  his  opinion  that  a  trans- 
mission of  10000  B.  t.  u.  per  square  foot  per  hour  is  all  that 
should  be  expected.  This  checks  closely  with  formula  83, 
which  gives  the  rate  of  transmission  9031  B.  t.  u.  per  square 
foot  per  hour. 


DISTRICT   HEATING  241 

The  following  empirical  formula  for  the  amount  of  heat- 
ing surface  in  a  heater  is  sometimes  used: 

Rt  =  .0944  Ws  (85) 

where  the  terms  are  the  same  as  before. 

APPLICATION. — Let  the  total  amount  of  exhaust  steam  avail- 
able for  heating  the  circulating  water  be  35000  pounds  per 
hour,  the  pressure  of  the  steam  in  the  condenser  be  atmos- 
pheric and  the  water  of  condensation  be  returned  at  180°; 
also,  let  the  circulating  water  enter  at  155°  and  be  heated  to 
180°.  These  values  are  good  average  conditions.  The  as- 
sumption that  the  pressure  within  the  condenser  is  atmos- 
pheric might  not  be  fulfilled  in  every  case,  but  can  be  ap- 
proached very  closely.  From  these  assumptions  find  the 
square  feet  of  surface  in  the  tubes. 

35000 

Formula   83,   Rt  =  =  3846   sq.   ft. 

9.1 

35000 

Formula  84,  Rt  =  =  4023  sq.   ft. 

8.7 

.Formula   85,  Rt  =  35000    X   .0944  =   3304   sq.    ft. 

1000  X35000 

•Sutcliffe  Rt  = =  3500  sq.  ft. 

10000 

If    3846    square    feet    be    the    accepted   value    it   will    call    for 
three  hea/ters  having   1282  square  feet  of  tube  surface  each. 

157.  Amount    of    Reheater    Tube     Surface    per    Engine 
Horse-Power: — Let    ws    be    the    pounds    of    steam    used    per 
/.  H.  P.  of  the  engine;  then  from  formula  83 

Rt   (per  I.  H.  P.)  = —  (86) 

9.1 

This  reduces  for  the  various  types  of  engines  as  follows: 

Simple    high    speed  34  -5-  9.1  =  3.74  square  feet 

"     medium          "  30  -r-  9.1  =  3.30 

"     Corliss  26  -r-  9.1  =  2.86 

Compound   high   "  26  -r-  9.1  =  2.86         "        '*  * 

"     medium     "  25  -i-  9.1  =  2.75 

"     Corliss  22  -r-  9.1  =  2.42 

158.  Amount    of   Hot    \Vater    Radiation    in    the    District 
that  can  be  Supplied  by  One  Square  Foot  of  Reheater  Tube 
Surface: — If    the    transmission    through    one    square    foot    of 
tube  .surface  be  K  (ts  —  *»)  =  9031  B.  t.  u.  per  hour  and  the 


242  HEATING  AND   VENTILATION 

amount    of    heat    needed    per    square    foot    of    radiation    per 
hour  =  8.33   X  25  =  208,  as  given  in  formula  74,  then 

9031 

Rw  (per  sq.  ft.  of  tube  surface)  = =  43.4  sq.  ft.       (87) 

208 

159.  Some  Important  Relieater  Details: — Inlet  and  outlet 
pipes. — Having  three  heaters  in  the  plant,  it  seems  rea- 
sonable that  each  heater  should  be  prepared  for  at  least  one- 
third  of  the  water  credited  to  the  exhaust  steam.  From 
Art.  151  this  is  140000  -i-  3  =  46667  gallons  =  10800000  cubic 
inches  per  hour.  The  velocity  of  the  water  entering  and 
leaving  the  heater  may  vary  a  great  deal,  but  good  values 
for  calculations  may  be  taken  between  5  and  7  feet  per 
second.  Assuming  the  first  value  given,  we  have  the  area 
of  the  pipe  =  10800000  -f-  (5  X  12  X  3600)  —  50  square  inches, 
and  the  diameter  8  inches. 

The  size  of  the  reheater  shell. — Concerning  the  velocity 
of  the  water  in  the  reheater  itself,  there  may  be  differences 
of  opinion;  100  feet  per  minute  will  be  a  good  value  to  use 
unless  this  value  makes  the  length  of  the  tube  too  great  for 
its  diameter.  If  this  is  the  case  the  tube  will  bend  from 
expansion  and  from  its  own  weight.  At  this  velocity  the 
free  cross  sectional  area  of  the  tubes,  assuming  the  water 
to  pass  through  the  tubes  as  in  Fig.  116,  will  be  150  square 
inches.  If  the  tubes  be  taken  %  inch  outside  diameter, 
with  a  thickness  of  17  B.  W.  G.,  and  anranged  as  usual  in 
such  work,  it  will  require  about  475  tubes  and  a  shell  diam- 
eter of  approximately  30  inches.  If  the  inner  surfa.ee  of  the 
tube  be  taken  as  a  measurement  of  the  heating  surface  and 
the  total  surface  be  1282  square  feet,  the  length  of  the  re- 
heater  tubes  will  be  approximately  16  feet. 

The  ratio  of  the  length  of  the  tube  to  the  diameter  is, 
in  this  case,  256,  about  twice  as  much  as  the  maximum  ratio 
used  by  some  manufacturers.  It  will  be  better,  therefore, 
to  increase  the  number  of  tubes  and  decrease  the  length. 
With  a  velocity  of  the  water  at  50  feet  per  minute,  the 
values  will  be  approximately  as  follows:  free  cross  sec- 
tional area  of  the  tubes,  300  square  inches;  number  of  tubes, 
950;  diameter  of  shell,  40  inches;  length  of  tubes,  8  feet. 
These  values  check  fairly  well  and  could  be  used. 

The  size  of  exhaust  steam  connection. — To  calculate  this,  use 
the  formula 

144  Q* 
A  =  (88) 


DISTRICT    HEATING  243 

where  Q«  =  volume  of  steam  in  cubic  feet  per  minute,  V  = 
velocity  in  feet  per  minute,  and  A  =  area  of  pipe  in  square 
inches.  When  applied  to  the  reheater  using  35000  pounds 
of  steam  per  hour,  at  26  cubic  feet  per  pound  and  at  a  veloc- 
ity through  the  exhaust  pipe  of  6000  feet  per  minute,  it  gives 

144  X  35000  X  26 

=  360  sq.  in    =  22  in.  dia. 


60  X  6000 
Try  also,  from  Carpenter's  H.  &  V.  B.,  page  284 


V 


1.23  (89) 

Allowing  30  pounds  of  steam  per  H.  P.  hour  for  non-condens- 
ing engines  we  ihave  35000  -j-  30  =  1166  horse-power;  then 
applying  the  above  we  obtain  d  =  16  inches.  Comparing 
the  two  formulas,  88  and  89,  the  first  will  probably  admit  of 
a  more  general  application.  The  velocity  6000  for  exhaust 
steam  may  be  increased  to  8000  for  very  large  pipes  and 
should  be  reduced  to  4000  for  small  pipes.  In  the  above 
applications  a  20  inch  pipe  will  suffice. 

The  return  pipe  for  condensation.  —  The  diameter  of  the  pipe 
leading  to  the  condenser  pump  will  naturally  be  taken  from 
the  catalog  size  of  the  pump  installed.  This  pump  would 
be  selected  from  capacities  as  guaranteed  by  the  respective 
manufacturers  and  should  easily  be  capable  of  handling  the 
amount  of  water  that  is  condensed  per  hour. 

The  value  of  a  high  pressure  steam  connection.  —  If  desired, 
•the  reheater  may  also  be  provided  with  a  high  pressure 
steam  connection,  to  be  used  when  the  exhaust  steam  is  not 
sufficient.  This  steam  is  then  used  through  a  pressure-re- 
ducing valve  which  admits  the  steam  at  pressures  varying 
from  atmospheric  to  5  pounds  gage.  There  is  some  question 
concerning  the  advisability  of  doing  this.  Some  prefer  to 
install  a  high  pressure  steam  heater,  as  in  Art.  160,  to  be 
used  independently  of  the  exhaust  steam  heaters.  This 
removes  all  possibility  of  having  excessive  back  pressure 
on  the  engine  piston,  as  is  sometimes  the  case  where  high 
pressure  steam  is  admitted  with  the  exhaust  steam. 

It  has  been  the  experience  of  some  who  have  operated 
such  plants  -that  where  more  heat  is  needed  than  can  be 
supplied  by  the  exhaust  steam,  it  is  better  to  resort  to  heat- 
ing boilers  and  economizers,  than  to  use  high  pressure  steam 
for  heating. 


244 


HEATING  AND   VENTILATION 


160.  High  Pressure  Steam  Heater:— When  this  heater  Is 
used  it  is  located  above  the  boiler  so  that  all  the  condensa- 
tion freely  drains  back  to  the  boilers  by  gravity  as  in  Fig. 
117.  In  calculating  the  tube  surface,  use  formula  82  with 
the  full  value  of  the  steam  and  the  steam  temperatures 
changed  to  suit  the  increased  pressure.  Such  a  heater  as 
this  gives  good  results. 


Fig.  117. 


161.  Circulating  Pumps: — Two  types  of  pumps  are  in 
general  use:  centrifugal  and  reciprocating.  Each  type  is 
somewhat  limited  in  its  operation.  The  centrifugal  pump 
has  difficulty  in  operating  against  high  heads  and  the  recip- 
rocating pump  is  very  noisy  when  running  at  a  high  piston 
speed.  Since  each  type  is  in  successful  operation  in  many 
plants,  no  comparisons  will  be  made  between  them  further 
than  to  say  that  the  former,  being  operated  by  a  steam  en- 
gine, may  be  run  more  economically  than  the  latter  because 
of  the  possibilities  of  using  the  steam  expansively.  It  will 


DISTRICT   HEATING  245 

be  noted,  however,  that  this  same  steam  is  to  be  used  in  the 
exhaust  steam  heaters  for  warming  the  circulating  water 
and  hence  there  would  be  little,  if  any,  direct  loss  from  this 
source  in  the  use  of  the  reciprocating  pump. 

Having  given  the  maximum  amount  of  water  to  be 
circulated  per  hour,  consult  trade  catalogs  and  select  the 
number  of  pumps  and  the  size  of  each  pump  to  be  installed. 
The  sizes  of  the  pumps  can  easily  be  determined  when  the 
number  of  them  has  been  decided  upon.  This  latter  point 
is  one  upon  which  a  difference  of  opinion  will  probably  be 
found.  No  exact  rule  can  be  applied.  In  a  plant  of,  say 
not  more  than  150000  square  feet  of  radiation  (150000  gal- 
lons of  water  per  hour,  or  3  million  gallons  for  twenty-four 
hours),  some  designers  would  put  in  three  pumps,  each 
having  1.5  million  gallons  capacity;  in  which  case  one  pump 
could  be  cut  out  for  repairs  and  the  other  two  would  be 
able  to  care  for  the  service  temporarily.  Other  designers 
would  use  four  pumps  at  about  one  million  gallons  each. 
The  fewer  the  pumps  installed,  in  any  case,  the  greater 
should  be  the  capacity  of  each.  The  following  values  will 
be  found  fairly  satisfactory: 

1  Pump.  Cap.  =  (1  to  1.25)  times  max.  requirem't  of  system 

2  Pumps.    "      (each)   =  .75  "            "                               "         " 
3 'Pumps.     "            "       =  .5  "                "              "         " 
4  Pumps.     "           "       =  .3  "            "                "              "         " 

Having  given  the  capacity  of  each  pump  in  gallons  of 
water  per  minute,  the  size,  the  horse-power  and  the  steam 
consumption  of  each  pump  can  be  calculated.  In  obtaining 
the  size  of  the  pump  it  will  be  necessary  to  know  the  speed, 
V,  of  the  piston  in  feet  per  minute,  the  strokes,  N,  per  minute 
and  the  per  cent,  of  slip,  8  (100  per  cent.  —  S,  where  S  =  hy- 
draulic efficiency).  The  speed  varies  between  100,  for  small 
pumps,  and  75,  for  large  pumps.  The  strokes  vary  between 
200,  for  small  pumps,  and  40,  for  large  pumps,  and  the  slip 
varies  between  5  and  40  per  cent.,  depending  upon  the  fit  of 
the  piston  and  the  valves.  In  pumps  that  have  been  in  serv- 
ice for  some  time  the  slip  will  probably  average  20  per  cent. 

The  cross  sectional  area  of  the  water  cylinder  in  square 
inches  is 

cubic  inches  pumped  per  minute 

W.  C.  A.    = (90) 

S  X   F  X   12 


246  HEATING  AND   VENTILATION 

from  which  we  may  obtain  the  diameter  of  the  water  cyl- 
inder. 

The  steam  cylinder  area  is  usually  figured  as  a  certain 
ratio  to  that  of  the  water  cylinder  area,  as 

8.  C.  A.  =  (1.5  to  2.5)    X  W.   C.  A.  (91) 

from  which  we  may  obtain  'the  diameter  of  the  steam  cylin- 
der. 

The  length  of  the  stroke,  L,  in  inches,  may  be  obtained 
from  the  speed  and  .the  number  of  strokes  such  that 

12   V 
L  =  (92) 

N 

All  direct  acting  steam  pumps  are  designated  by  diam- 
eter of  steam  cylinder  X  diameter  of  water  cylinder  X  length 
of  stroke,  as 

14"  X  12"  X   18" 

Duplex  pumps  have  twice  the  capacity  of  single  pumps 
.having  the  same  sized  cylinders. 

To  find  the  indicated  horse-power,  I.  H.  P.,  of  the  pumps, 
reduce  the  pressure  head,  p,  in  pounds  per  square  inch,  to 
pressure  head  in  feet,  7i;  multiply  this  by  the  pounds  of 
water,  W,  pumped  per  minute  and  divide  the  product  by 
33000  times  the  mechanical  efficiency,  E. 

w  n 

L  H.  P.  = (93) 

33000  E 

To  reduce  from  pressure  head  in  pounds  to  pressure 
head  in  feet,  divide  the  pressure  head  in  pounds  by  weight 
of  a  column  of  water  one  square  inch  in  area  and  one  foot 
high.  The  general  equation  for  this  is 

144  p 
w 

where  w  =  the  weight  of  a  cubic  foot  of  water  at  the  given 
temperature  and  p  =  differential  pressure  in  pounds  per 
square  inch. 

In  pump  service  of  this  kind  the  pressure  head,  p, 
against  which  the  pump  is  acting,  is  not  the  result  of  the 
static  head  of  water  in  the  system  but  is  due  to  the  inertia 
of  the  water  and  to  the  resistance  to  the  flow  of  water 


DISTRICT   HEATING  247 

through  the  piping  system  and  the  heaters.  This  frictional 
resistance  may  be  calculated  as  shown  in  Art.  147.  Read 
this  part  of  the  work  over  carefully. 

For  an  illustration  of  combined  pressure  head,  p,  and 
friction  head,  hf,  see  Art.  164  on  boiler  feed  pumps.  Having 
found  the  /.  H.  P.  of  any  pump,  multiply  it  by  the  steam  con- 
sumption per  /.  H.  P.  hour  and  the  result  will  be  the  steam 
consumption  of  the  pump.  This  exhaust  steam  will  be  con- 
sidered a  part  of  the  general  supply  when  figuring  the  size 
of  the  exha,ust  steam  heaters  in  the  system. 

The  mechanical  efficiency,  E,  of  piston  pumps  depends 
upon  the  condition  of  the  valves  and  upon  the  speed,  and 
varies  from  90  per  cent,  in  new  pumps,  to  50  per  cent,  in 
pumps  that  are  badly  worn.  A  fair  average  would  be  70 
per  cent. 

The  steam  consumption  for  reciprocating,  simple  and 
duplex  non-condensing  pumps  would  approximate  100  to 
200  pounds  of  steam  per  /.  //.  P.  hour — the  greater  values  re- 
ferring to  the  .slower  speeds. 

162.  Centrifugal  Pumps: — Centrifugal  pumps  are  of 
two  classifications,  the  Volute  and  the  Turbine.  The  prin- 
ciples upon  which  each  operate  are  very  similar.  The  ro- 
tating impeller,  or  rotor,  with  curved  blades  draws  the 
-water  in  at  the  center  of  the  pump  and  delivers  it  from  the 
circumference.  The  rotor  is  enclosed  by  a  cast  iron  case- 
ment which  is  shaped  more  or  less  to  fit  the  curvature  of 
,the  edges  of  the  blades  on  the  rotor.  Centrifugal  pumps 
are  used  where  large  volumes  of  water  are  required  at  low 
heads.  They  are  used  in  city  water  supply  systems,  in  cen- 
tral station  heating  systems,  in  condenser  iservice,  in  irri- 
gation work  and  in  many  other  places  where  the  pressure 
head  operated  against  is  not  excessive.  The  efficiency  of 
the  average  centrifugal  pump  is  from  65  to  80  per  cent., 
75  per  cent,  being  not  uncommon.  In  places  where  such 
pumps  are  used  the  head  is  usually  below  75  feet,  although 
some  types,  when  direct  connected  to  high  speed  motors, 
are  capable  of  operating  against  heads  of  several  hundred 
feet. 

iSome  of  the  advantages  of  centrifugal  pumps  over  hor- 
izontal ireciprocating  pumps  are:  low  first  cost,  simplicity, 
few  moving  parts,  compactness,  uniform  flow  and  pressure 
of  water,  freedom  from  shock,  possibilities  of  direct  connec- 


248  HEATING  AND   VENTILATION 

tion  to  high  speed  motors  and  the  ability  to  handle  dirty 
water  without  injuring  the  pump. 

One  of  the  advantages  of  piston  pumps  over  centrifugal 
pumps  is  the  fact  that  they  are  more  positive  in  their 
operation  and  work  against  higher  heads. 

Centrifugal  pumps,  when  connected  to  engine  and  tur- 
bine drives,  benefit  by  the  expansion  of  the  steam  and  are 
much  more  economical  than  the  direct  acting  piston  pump, 
which  takes  steam  at  full  pressure  for  nearly  the  entire 
stroke.  The  amount  of  steam  used  in  the  pumps  in  central 
station  work,  however,  is  not  a  serious  factor,  since  all  of 
the  heat  in  the  steam  that  is  not  used  in  propelling  the 
water  through  the  mains  is  used  in  'the  heaters  to  increase 
the  temperature  of  the  water. 

The  sphere  of  usefulness  of  the  centrifugal  pump  in 
central  station  heating  is  increasing.  The  direct  acting 
piston  pump,  when  operating  at  fairly  high  speeds,  causes 
hammering  and  pounding  in  the  transmission  lines,  and 
these  noises  are  sometimes  conveyed  to  the  residences  and 
become  annoying  to  the  -occupants.  This  feature  is  not  so 
noticeable  in  the  operation  of  the  centrifugal  pump. 

APPLICATION. — In  Art.  145  assume  the  capacity  of  the  plant, 
10  business  squares  and  21  residence  squares,  to  require 
184500  gallons  of  water  per  hour;  the  same  to  be  pumped 
against  a  pressure  head,  Art.  147,  of  50 — 5  pounds,  by 
horizontal,  direct  acting  piston  pumps.  Assume  also  the 
steam  consumption  of  the  pumps  to  be  100  pounds  per  /.  H.  P. 
hour  and  the  average  temperature  of  the  water  at  the 
pumps  to  be  (180  +  155)  -f-  2  =  167.5  degrees.  Apply  for- 
mula 93,  where  h  =  calculated  total  friction  head  for  the 
longest  line  in  the  system  (this  is  designated  by  hf  in  Art. 
147),  or  where  p  =  total  difference  between  the  incoming 
and  the  outgoing  pressures.  With  the  weight  of  a  cubic 
foot  of  water  at  167.5  degrees  =  60.87  pounds  and  with 
p  =  45,  we  have  h  =  106.5  feet,  and  the  indicated  horse-power 
of  the  pumps,  assuming  65  per  cent,  mechanical  efficiency,  is 

184500  X  8.33  X  106.5 

/.  H.  P.  =  -  =  127.2 

33000  X.65  X  60 

From  this  the  steam  consumption  will  probably  be  12720 
pounds  per  hour. 

If  centrifugal  pumps  were  selected,  the  horse-power 
would  be  calculated  from  the  same  formula,  but  the  steam 


DISTRICT   HEATING  249 

consumption  would  probably  be  30  to  40  pounds  of  steam 
per  horse-power  hour  because  of  the  expansive  working  of 
the  steam. 

163.  City  Water  Supply  Pumps: — Horizontal,  direct  act- 
ing duplex  pumps  for  use  on  city  water  supply  service  are 
the  same  as  those  used  to  circulate  the  water  in  heating 
systems;  hence,  the  foregoing  descriptions  apply  here.  The 
7.  77.  P.  of  the  city  water  supply  pumps  would  be  calculated 
by  use  of  formula  93.  If  the  pumps  lifted  the  water  from 
the  wells,  as  would  probably  be  ithe  case,  the  suction  pres- 
sure would  be  negative  and  would  be  added  to  the  force 
pressure. 

APPLICATION. — Assume  the  pressure  in  the  fresh  water 
mains  60  pounds  and  the  suction  pressure  10  pounds; 
therefore,  p  —  60  —  ( — 10)  —  70  pounds,  and  with  the  water 
at  65  degrees,  h  =  144  X  70  -i-  62.5  =  161  feet.  These  pumps 
are  each  rated  at  1.5  million  gallons  in  24  hours,  and  deliver 
62500  X  8.33  =  520833  pounds  of  water  per  hour,  when  run- 
ning at  full  capacity.  Assuming  each  pump  to  deliver  75  per 
cent,  of  the  full  requirement  of  the  system,  the  total  amount 
of  water  pumped  per  hour  for  the  city  water  supply  would 
approximate  520833  -r-  .75  =  694444  pounds,  and  the  total 
average  horse-power  used  in  pumping  the  water  would  be 

694444  X  161 
7.  77.  P.  = 


60  X  33000  X.65 

With  100  pounds  of  steam  per  horse-power  hour,  this  would 
amount  to  8680  pounds  of  steam  available  per  hour  for  use 
in  heating  the  circulating  water. 

164.  Boiler  Peed  Pumps: — Horizontal  pumps  for  high 
pressure  boiler  feeding  are  selected  in  a  similar  way  to  the 
circulating  pumps  for  the  city  water  supply.  Such  units 
are  called  auxiliary  steam  units  and,  because  the  steam  re- 
quired is  small,  they  are  sometimes  piped  to  a  feed  water 
heater  for  heating  the  boiler  feed.  The  velocity  'Of  the  water 
through  the  suction  pipe  Is  about  200  feet  per  minute  and 
in  the  delivery  pipe  about  300  feet  per  minute.  The  piston 
speed,  the  strokes  per  minute  and  the  slip  would  be  very 
much  the  same  as  stated  under  circulating  pumps.  Such 
pumps  should  have  a  pumping  capacity  about  twice  as  great 
as  the  actual  boiler  requirements,  and  in  small  plants  where 
only  one  pump  is  needed,  the  installation  should  be  in 


250  HEATING   AND   VENTILATION 

duplicate.     The  sizes  of  the  cylinders  and  the  efficiencies  are 
about  as  stated  for  the  larger  circulating  pumps. 

In  determining  the  horse-power  of  a  boiler  feed  pump, 
four  resistances  must  be  overcome;  i.  e.,  pressure  head,  p, 
or  boiler  pressure;  suction  head,  hs;  delivery  head,  ha;  and 
the  friction  head,  Tit.  The  first  three  values  are  usually 
given.  The  friction  head  includes  the  resistances  in  all  pip- 
ing, ells  and  valves  from  the  supply  to  the  boiler.  The  fric- 
tion in  the  piping  may  be  taken  from  Table  37,  Appendix,  or 
it  may  be  worked  out  by  formula  70.  The  friction  in  the  ells 
and  valves  is  more  difficult  to  determine  and  is  usually  stated 
in  equivalent  length  of  straight  pipe  of  the  same  diameter. 
A  rough  rule  used  by  some  in  such  cases  is  as  follows: 
"to  the  length  of  the  given  pipe,  add  60  times  the  nominal 
diameter  of  the  pipe  for  each  ell,  and  90  times  the  diameter 
for  each  globe  valve,"  then  find  the  friction  head  as  stated 
above.  A  straight  flow  gate  or  water  valve  could  safely  be 
taken  as  an  ell.  For  simplicity  of  calculation,  all  of  the 
above  resistances  may  be  reduced  to  an  equivalent  head, 
such  that 

144  p 

he  = H  hd  +  h,  +  hf  (94) 

w 

where  w  =  weight  of  one  cubic  foot  of  water  at  the  suc- 
tion temperature,  w  may  be  obtained  from  Table  8,  Ap- 
pendix, and  hf  may  be  taken  from  Table  37.  The  horse-power 
by  formula  93  then  becomes,  if  W  —  pounds  of  water  pumped 
per  minute, 

W  Xhe 

I.  H.  P.  =  — (95) 

33000 # 

APPLICATION. — Let  p  =  125  pounds  gage,  w  =  62.5,  ha.  =  8 
feet,  7t»  ==  ~20  feet,  horizontal  run  'Of  pipe  from  supply  to 
pump  =  20  feet,  horizontal  run  of  pipe  from  pump  to  boiler 
=  30  feet;  also,  let  the  pump  supply  89000  pounds  of  water 
per  hour  to  the  boiler.  This  is  twice  the  capacity  of  the 
boiler  plant.  With  this  amount  of  water  at  the  usual  veloc- 
ity it  will  give  a  suction  pipe  of  4.5  inches  diameter,  and  a 
flow  pipe  of  4  inches  diameter.  Let  there  be  two  ells  and 
one  gate  valve  on  the  suction  pipe,  and  three  ells,  one  globe 
valve  and  one  check  valve  on  the  delivery  pipe.  We  then 
have  an  equivalent  of  107  feet  of  suction  pipe,  and  158  feet 
of  delivery  pipe.  Referring  to  Table  37,  hf  is  approxi- 
mately 7  feet,  and  the  total  head  is 


DISTRICT   HEATING  251 

144   X   125 


62.5 


+  8  +  20  +  7  =  323  feet. 


In  most  boiler  feed  pumps  it  is  considered  unnecessary 
to  determine  hf  so  carefully.  A  very  satisfactory  way  is  to 
obtain  the  total  head  pumped  against,  exclusive  of  the 
friction  head,  and  add  to  .it  5  to  15  per  cent.,  depending 
upon*  the  complications  in  the  circuit.  Substituting  th« 
above  in  formula  95,  we  obtain 

89000   X   323 

/.  II.  P.  =  —  —.  --  =  22.3 

60   X   33000   X  .65 

Work  out  the  value  of  hf  by  formula  70  and  see  how 
nearly  it  checks  with  the  above., 

165.  Boilers:  —  A  number  of  boilers  will  necessarily  be 
installed  in  a  plant  of  th'*  kind,  and  a  good  arrangement  is 
to  have  them  so  piped  with  water  and  steam  headers  that 
any  number  of  the  boilers  may  be  used  for  steaming  pur- 
poses and  the  rest  as  water  heaters.  They  should  also*  be  so 
arranged  that  any  of  the  boilers  may  be  thrown  out  of 
service  for  cleaning  or  repairs  and  stil'l  carry  on  the  work 
of  the  plant.  By  doing  this  the  boiler  plant  becomes  very 
flexible  and  each  boiler  is  an  independent  unit.  Any  good 
water  tube  boiler  would  serve  the  purpose,  both  as  a  steam- 
Ing  and  as  a  heating  boiler.  Where  the  boilers  are  used  as 
heaters,  the  water  should  enter  at  the  bottom  and  come  out 
at  the  top.  Where  the  water  enters  at  the  top  and  comes 
out  at  the  bottom,  the  excessive  heating  of  the  front  row  of 
tubes  retards  the  circulation  of  the  water  by  ithis  heat,  and 
produces  a  rapid  circulation  through  the  rear  tubes  where  the 
heat  is  the  least.  This  rapid  circulation  in  'the  rear  tubes  is 
not.  a  detriment,  but  it  is  less  needed  there  than  in  the-front 
ones.  It  would  be  decidedly  better  if  the  rapid  circulation  were 
in  the  front  row,  causing  the  heat  firom  the  fire  to  be  carried 
off  more  readily,  and  by  this  means  giving  less  danger  of 
burning  the  tubes.  In  the  latter  case  the  forced  circulation 
from  the  pumps  will  be  aided  by  the  natural  circulation 
from  the  heat  of  the  fire,  and  the  life  of  all  the  tubes  then 
becomes  more  uniform.  Fig.  118  shows  a  typical  header 
arrangement. 

Boilers  are  usually  classified  as  fire  tube  and  water  tube. 
Fire  tube  boilers  are  usually  of  the  mult  i  tubular  type,  having 
the  flue  gases  passing  through  the  tubes  and  water  sui> 


252  HEATING  AND  VENTILATION 

rounding  them.  Water  tube  boilers  have  the  water  passing- 
through  the  tubes  and  the  flue  gases  surrounding  them. 
The  heating  surface  of  a  boiler  is  composed  of  those  boiler 
plates  having  the  heated  flue  gases  on  one  side  and  the  water 
on  the  other.  A  boiler  horse-power  may  be  taken  as  follows: 

Centennial  Rating. 

One  B.  H.  P.  —  30  pounds  of  water  evaporated  from  feed 
water  at  100°  F.  to  steam  at  70  pounds  gage  pressure. 

A.  S.  M.  E.  Rating. 

One  B.  H.  P.  =  34.5  pounds  of  water  evaporated  from 
and  at  212°  F, 

In  laying  out  a  boiler  plant  some  good  approximations 
for  the  essential  details  are: 

One  B.  H.  P.  =  11.5  square  feet  of  heating  surface 

(multitubular  type). 
One  B.  H.  P.  —  10  square  feet  of  heating  surface 

(water  tube  type). 
One  B.  H.  P.  =  .33  square  foot  of  grate  surface 

(small   plant,   say  one  boiler). 
One  B.  H.  P.  =  .25  square  foot  of  grate  surface 

(medium  sized  plant,   say  500  H.  P.). 
One  B.  H,  P.  =  .20  square  foot  of  grate  surface 

(large  plants). 

Pounds  of  water  evaporated  per  square  foot  of  heating 
surface  per  hour  =  3  (approx.  value). 

106.  Square  Feet  of  Hot  Water  Radiation  that  can  be 
Supplied  on  a  Zero  Day  by  One  Boiler  Horse-Power  when  the 
Boiler  is  Used  as  a  Heater: — Assuming  that  the  coal  used  in 
the  plant  has  a  heating  value  of  13000  B.  t.  u.  per  pound, 
and  that  the  efficiency  of  the  boiler  is  60  per  cent.,  each 
pound-  of  coal  will  transmit  to  the  water  7800  B.  t.  u.  Since 
each  pound  of  water  takes  up  25  B.  t.  u.  on  its  passage 
through  the  heating  boiler,  one  pound  of  coal  will  heat  312 
pounds,  or  37.5  gallons  <of  water.  This  is  equivalent  to 
supplying  heat,  under  extreme  conditions  of  heat  loss,  to 
37.5  square  feet  of  radiation  for  one  hour.  One  boiler  horse- 
power, according  to  Art.  165,  is  equivalent  to  the  expendi- 
ture of  969.7  X  34.5  =  33455  B.  t.  u.  Now  since  each  pound 
of  coal  transfers  to  the  water  7800  B.  t.  u.,  one  boiler  horse- 
power will  require  33455  -r-  7800  =  4.28  pounds  of  coal.  If, 
then,  the  burning  of  one  pound  of  coal  will  supply  37.5 
square  feet  of  hot  water  radiation  for  'One  hour,  one  boiler 


DISTRICT   HEATING  253 

horse-power  will  supply  4.28  X  37.5  =  160  square  feet  for  one 
hour,  and  a  100  H.  P.  boiler  will  supply  16000  square  feet 
of  water  radiation  in  the  district  for  the  same  time.  These 
figures  have  reference  to  boilers  under  good  working  con- 
ditions and  probably  give  average  results. 

107.  Square  Feet  of  Hot  Water  Radiation  in  the  District 
that  can  be  Supplied  on  a  Zero  Day  by  an  Economizer  Lo- 
cated in  the  Stack  Gases  between  the  Boilers  and  the  Chim- 
ney:— In  order  to  make  this  estimate  it  is  necessary  first  to 
know  the  horse-power  of  the  boilers,  the  amount  of  coal 
burned  per  hour,  the  pounds  of  gases  passing  through  the 
furnace  per  hour  and  the  heat  given  off  from  'these  gases 
to  the  circulating  water  through  the  'tubes. 

APPLICATION. — Let  C  =  pounds  of  coal  burned  per  hour  = 
boiler  horse-power  X  pounds  of  coal  per  boiler  horse-power 
hour,  Wa  =  pounds  of  air  passed  through  the  furnace  per 
pound  of  fuel  burned,  s  =  specific  heat  of  the  gases,  U  =  tem- 
perature of  gases  leaving  boiler,  ts  =  temperature  of  gases 
leaving  economizer,  tw  —  temperature  of  water  entering 
economizer  and  tf  =  'temperature  of  water  leaving  the  econo- 
mizer. Then,  if  8.33  pounds  of  water  will  supply  one  square 
foot  of  radiation  for  one  hour  we  have 

s  X  (C  X  Wa  +  C)  X  (*»  —  ts) 

Rw  =  (96) 

8.33  X  (tf  —  tw) 

From  a  previous  statement,  44500  pounds  of  steam  per 
hour  are  generated  in  the  steam  boiler  plant  at  a  pressure 
of  125  pounds  gage.  To  find  the  boiler  horse-power  let  the 
total  heat  of  the  steam,  above  32°  at  125  pounds  gage,  be 
1191.8  B.  t.  u.,  and  let  the  temperature  of  the  incoming  feed 
wiater  to  the  boilers  be  60  degrees.  (In  most  cases  the  feed 
water  will  be  at  a  higher  temperature,  but  since  it  will  occa- 
sionally be  as  low  as  60  'degrees,  this  value  will  be  a  fair 
one.)  The  heat  put  into  a  pound  of  steam  under  these  con- 
ditions is  1191.8  —  (60  —  32)  =  1163.8  B.  t.  u.,  and  in  44500 
pounds  it  will  be  51789100  B.  t.  u.  Since  one  horse-ipower  of 
boiler  service  is  equivalent  to  33455  B.  t.  u.,  we  will  need 
51789100  -J-  33455  =  1548  boiler  horse-power.  This  horse- 
power will  take  care  of  all  the  engines  and  puimps  im  the 
plant.  If  the  coal  used  contains  13000  B.  t.  u.  per  pound 
and  the  boilers  have  60  per  cent,  efficiency,  then  7800  B.  t.  u. 
will  be  given  to  the  water  per  pound  of  fuel  burned,  and 


254  HEATING  AND   VENTILATION 

the  amount  of  coal  burned  per  hour  will  be  51789100  -=-  7800 
=  6640  pounds.  This  gives  6640  -r-  1548  =  4.3  pounds  of  fuel 
per  boiler  horse-power  hour,  and  6.7  pounds  of  water  evap- 
orated per  pound  of  fuel.  If  the  flue  gases  have  12  per  cent. 
OO2,  there  are  used  according  to  experimental  data,  about 
21  pounds  of  air  or  22  pounds  of  the  gases  of  combustion, 
per  pound  of  fuel  burned.  This  is  equivalent  to  6640  X  22 
=  146080  pounds  of  flue  gases  total.  Suppose  now  that  these 
gases  leave  the  furnace  for  the  chimney  at  a  temperature 
of  550  degrees  F.,  that  the  economizer  drops  the  tempera- 
ture of  the  gases  down  to  350  degrees  (a  condition  which  is 
very  reasonable)  and  that  the  specific  heat  of  the  gases  Is 
about  .22,  we  have  146080  X  .22  X  (550  —  350)  =  6427520 
B.  t.  u.  given  off  from  the  gases  per  hour  in  passing  -through 
the  economizer  (see  numerator  in  formula  96).  This  heat 
is  taken  up  by  the  circulating  water  in  passing  through  the 
economizer  toward  the  outgoing  main.  Now  if  the  water, 
as  it  returns  from  the  circulating  system,  enters  the  econo- 
mizer at  155  degrees,  and  leaves  at  180  degrees,  we  will  have 
6427520  -7-  (180  —  155)  —  257100  pounds  of  water  heated  per 
hour.  This  is  equivalent  to  supplying  257100  -^  8.33  =  30864 
square  feet  of  radiation  per  hour  when  the  plant  is  running 
at  its  peak  load.  Taking  the  "pounds  of  steam  per  hour"  in 
the  above  as  the  only  variable  quantity,  we  are  fairly  safe 
in  saying  that  the  heat  in  the  chimney  gases  from  one  horse- 
power of  .steaming  boiler  service  will  supply,  through  an 
economizer,  30864  -r-  1548  =  20  square  feet  of  radiation  in  the 
district.  In  plants  where  only  7  pounds  of  water  are  allowed 
to  each  square  foot  of  radiation  per  hour,  .this  becomes  23.8 
square  feet  of  radiation  instead. 

168.  Square  Feet  of  Economizer  Surface  Required  to 
Heat  the  Circulating  Water  in  Art.  167: — Let  K  =  the  coeffi- 
cient of  heat  transmission  through  clean  cast  iron  tubes  and 
E  —  the  efficiency  of  the  tube  surface  when  in  average  serv- 
i-ce,  also  let  the  terms  for  the  temperatures  of  the  gases 
and  the  circulating  water  be  as  given  in  Art.  167,  then 

Heat  trans,  per  hour  from  gases  to  water 

Re    =   (97) 

KXEX 

\          2 

This  formula  assumes  that  the  rate  of  heat  flow  through 
the  tubes  is  -the  same  at  all  points.  As  a  matter  of  fact  this 
rate  changes  slightly  as  the  water  becomes  heated,  but 


DISTRICT   HEATING  255 

the  error  is  not  worth  mentioning  in  such  a  formula,  where 
the  efficiency  of  the  surface  may  be  anything  from  100  per 
cent,  in  new  tubes,  to  as  low  as  30  or  40  per  cent,  for  old 
ones. 

APPLICATION. — Let  K  =  1  and  E  =  A,  then 

6427520 

Re   —  =    8125  sq.  ft. 

/      550  +  350  180  +  155    \ 

7  X.4  X  ( •    ) 

V  2  2  / 

With  12-<square  feet  of  surface  per  tube  this  gives  677  tubes. 

169.  Square  Feet  of  Economizer  Surface  to  Install  when 
the   Economizer   is   to   be   Used  to   Heat   the   Feed   Water  for 
the   Steaming  Boilers: — If   30   pounds   of   feed    water   are   fed 
to   the   boiler  per  ihorse-power   hour,   and  if  K  —  7,  E  =  .4, 
tb  =  550,   t»  =  350,  tf  =  250,   and   tw  =  90    (about  the  lowest 
temperature  at  which   water  should  enter  the   economizer), 
then  the  square  feet  of  surface  per  horse-power  is 

30  X  (250  —  90) 

Re  =• =  6.1  sq.  ft. 

/    550  +  350  250  +  90      \ 

7  X  .4  X    I ) 

V  2  2  / 

170.  Total  Capacity  of  the  Boiler  Plant  and  the  Number 
of  Boilers   Installed: — The   following   discussion   on   the   size 
of  the   boiler  plant   is   purely   for   illustrative  purposes   and 
is   intended   to   show   how    such   problems   may   be   analyzed. 
In  most  cases  the  exhaust  steam,  and  the  economizer,  if  used, 
will   fall   far    short   of   supplying   the    total   radiation    in   the 
district,    especially  when    the   electrical  'Output   is   light  and 
the  weather  is  cold.   Suppose   it   be   desired  to   install   extra 
boilers  to  be  used  as  heaters  for  the  radiation  not  supplied 
from  these   two   sources.      To    determine   the   amount   of   ex- 
tra boilers,   find  'the  amount   of   radiation   to   be  supplied  by 
the    exhaust    steam    and    the    economizer    and    subtract    this 
from   the   total   radiation.      The    difference   must   be   supplied 
by  boilers  used  as  heaters.     It  is  probably  not  safe  to  esti- 
mate too  closely   on  the  aimount  of   exhaust  steam  given  to 
the  heating  system.     The  maximum  amount  of  44500  pounds 
per   hour   was   obtained,    in   this   case,    by   pumping   one   gal- 
Ion  of  water  per  hour  for  each  square  foot  of  radiation  and 
by   pumping   city   water,    in    addition   to   that  'Obtained   from 
the  engines.     In  heating,  a  less  amount  of  water  than  this 
may  be   circulated   eveji   on  the   coldest  day.      This   is  possi- 
ble,   first,    because    water   may   be   carried   at   a   higher   tern- 


256  HEATING  AND   VENTILATION 

perature  than  that  stated,  and  second,  because  there  may 
be  less  loss  of  heat  in  the  conduit,  thus  giving  more  heat  per 
gallon  of  water  to  the  radiation.  Again,  in  estimating  for 
a  city  water  supply,  the  demands  are  not  very  constant  and 
are  difficult  to  estimate.  In  this  one  design  it  was  thought 
that  44500  pounds  per  hour  was  a  very  liberal  allowance 
and  could  be  dropped  to  35000  pounds  (140000  square  feet 
of  radiation),  when  estimating  the  amount  of  radiation 
supplied  by  the  exhaust  steam. 

By  Pig.  113  it  will  be  seen  that  the  minimum  load  on  the 
steaming  boilers  carries  through  six  hours  out  of  the  entire 
twenty-four  and  that  the  exhaust  steam  at  this  time  drops 
to  22890  pounds  per  hour,  supplying  91560  square  feet  of 
radiation.  This  minimum  load  is  51  per  cent,  of  the  max- 
imum, and  66  per  cent,  of  the  amount  taken  as  an  average, 
i.  e.,  35000.  The  work  done  by  the  economizer  is  fairly  con- 
stant, .since  the  amount  of  economizer  surface  lost  by  the 
steaming  boilers  under  minimum  load  would  be  made  up 
by  the  additional  heating  boilers  'thrown  into  service.  On 
the  basis  of  35000  pounds  per  hour,  the  exhaust  steam  and  the 
stack  gases  together  would  heat  170960  square  feet  and 
there  would  be  left  13540  square  feet  (184500  —  20  X  1548 
—  4  X  35000),  to  be  heated  by  additional  boilers.  Under 
minimum  load  this  would  be  approximately  122500,  leaving 
62000  square  feet  to  be  heated  by  additional  boilers.  If  one 
boiler  horse-power  supplies  160  square  feet  of  radiation, 
then  it  would  require  84  and  387  boiler  horse-power  re- 
spectively to  supply  the  deficiency  and  the  total  horse-power 
needed  'in  each  case  would  be  1632  and  1935.  A  more  satis- 
factory analysis,  however,  is  the  following  which  is  worked 
on  the  basis  of  44500  pounds  per  hour. 

Let  Wt  =  total  number  of  pounds  of  steam  used  in  the 
plant  per  hour  =  approximate  number  of  pounds  of  exhaust 
steam  available  for  heating  the  circulating  water  per  hour; 
We  =  equivalent  number  of  pounds  of  steam  evaporated  from 
and  at  212°;  X  =  total  heat,  above  32',  in  one  pound  of  dry 
steam  at  the  boiler  pressure;  q'  =  total  heat,  above  32°,  in 
one  pound  of  feed  water  entering  the  boiler;  then,  if  the 
latent  heat  of  steam  at  atm>ospheric  pressure  =  969.7  B.  t.  u., 
we  have 

Ws  (\  —  q') 

We    ~ (98) 

969.7        • 


DISTRICT   HEATING  257 

and  the  corresponding  boiler  horse-power  needed  as  steam- 
ing boilers  will  be 

We 

B».  H.  P,  — (99) 

34.5 

Next,  the  radiation  in  the  district  that  can  be  supplied 
by  the  exhaust  steam  is  Rw  =  4  Ws,  and  the  amount  sup- 
plied by  the  economizer  is  Re  =  20  X  B.  H.  P.  From  which 
we  may  obtain  the  capacity  of  the  heating  boilers,  as 

Total  Radiation  —  4  Ws  —  20  B.  II.  P. 

B*.  H.  P.  =  — (100) 

160 

The  total  boiler  horse-power  of  the  plant  is,  therefore,  the 
sum  of  Bs.  H.  P.  and  Bw.  H.  P.  To  obtain  formula  100  for  any 
specific  case  one  must  consider  the  maximum  and  minimum 
conditions  of  the  steaming  boiler  plant.  Let  Ws  (max)  = 

•maximum  exhaust  staam,  and  Ws  (min)  =  minimum  exhaust 
steam.  Then  for  the  two  following  conditions  we  have, 
Case  1,  where  the  steaming  and  heating  boilers  are  independent  of 
each  other,  the  total  'boiler  horse-power  installed  =  Bs.  H.  P. 
+  [total  radiation  —  4  Ws  (min)  —  20  X  B.  H.  P.  in  use]  -f- 
160.  Also,  Case  2,  where  a  part  or  all  of  the  steaming  boilers  are 
piped  for  both  steaming  and  water  service,  the  total  boiler  horse- 
power installed  =  Bs.  H.  P.  +  [total  radiation  —  4  W8  (max) 
—  20  X  B.  H.  P.  in  use]  -=-  160.  It  will  be  noticed  that  ithe  last 
term  representing  the  economizer  service  is  simply  stated 

'as  boiler  horse-power  and  no  distinction  is  made  between 
steaming  or  heating  service.  This  term  is  difficult  ito  esti- 
mate to  an  exact  figure  because  it  should  be  the  total  horse- 
power in  use  at  any  one  time,  both  steaming  and  heating, 
and  this  can  only  be  'Obtained  by  approximation.  It  makes 
no  difference  what  service  the  boiler  may  be  used  for,  the 
W'ork  of  the  economizer  is  practically  the  same.  Probably 
the  most  satisfactory  way  is  to  substitute  the  value  of 
Bs.  H.  P.  for  B.  H.  P.  in  the  economizer  and  get  the  approxi- 
mate total  horse-power,  then  if  this  approximate  total  horse- 
power differs  very  much  from  that  actually  needed,  other 
trials  may  be  made  and  new  values  for  the  total  horse-power 
obtained  until  the  equation  is  satisfied. 


258  HEATING  AND   VENTILATION 

APPLICATION. — Let  Ws  =  pounds  of  exhaust  steam,  X  = 
1191.8  (125  pounds  gage  pressure),  and  q'  =  28  (feed  water 
at  60°);  then  when  Ws  =  44500 

We  =  53400 

Bs.  H.  P.  =  1548 

184500  —  4  X  22890  —  20  X  1548 

Dw.  H.  P.  Case  1  —  =  387 

160 

184500  —  4  X  44500  —  20  X  1548 

Dw.  II.  P.  Case  2  = =  —153 

160 

This  shows  that  there  is  an  excess  of  waste  heat  in  Case  2, 
making  a  total  boiler  horse-power,  Case  1,  =  1935  and  Case 
2,  =  1548.  Investigating  Case  1  to  see  what  error  was  intro- 
duced by  using  1548  in  the  economizer,  we  find  approximately 
800  horse-power  of  steam  boilers  in  use,  and  the  total  horse- 
power to  be  1187,  which  is  about  360  horse-power  on  the 
unsafe  side.  Substitute  again  and  check  results.  Case  2  Is 
reasonably  close.  In  any  case  'the  most  economical  size  of 
boiler  plant  to  install  in  a  plant  requiring  both  steaming  and 
heating  boilers  is  one  where  at  least  a  part,  if  not  all,  of  the 
boilers  are  piped  so  as  to  be  easily  changed  from  one  system 
to  the  other.  By  such  an  arrangement  the  capacity  may  be 
made  the  smallest  possible.  After  obtaining  'the  theoretical 
size  of  the  plant,  it  would  be  well  to  allow  a  small  margin 
in  excess  so  that  one  or  two  boilers  may  be  thrown  out  of 
commission  for  repairs  and  cleaning  without  interfering 
with  the  working  of  the  plant.  Case  2  seems  to  be  the  better 
arrangement.  Assuming  1800  total  boiler  horse-power  we 
might  very  well  put  in  six  300  H.  P.  boilers  arranged  in  three 
batteries. 

171.  Cost  of  Heating  from  a  Central  Station  (Direct 
Firing): — It  wall  be  of  interest  in 'this  connection  to  estimate 
approximately  the  cost  in  supplying  heat  by  direct  firing  to 
one  square  foot  of  hot  water  radiation  per  year  from  the 
average  central  station.  In  doing  this  make  the  boiler  as- 
sumptions to  be  the  same  as  Art.  166.  Take  coal  at  13000 
B.  t.  u.  per  pound,  2000  pounds  per  ton,  and  a  boiler  effi- 
ciency of  60  per  cent.  Wiater  enters  the  boiler  at  155  degrees 
from  the  returns,  and  is  delivered  to  the  mains  at  180  de- 
grees'. From  the  value  of  the  ooal  as  stated,  we  have 
15600000  B.  t.  u.  per  ton  given  off  to  the  water.  This  is 


DISTRICT   HEATING 


259 


It 


POWER  PLANT  LAYOUT. 
Fig.   118. 


260  HEATING  AND  VENTILATION 

equivalent  to  heating  624000  pounds,  or  74910  gallons,  of 
water.  If  one  ton  of  coal  costs  $2.00  at  the  plant,  we  have 

200  -h  74910  =  .0027  cents 

This  represents  the  amount  paid  to  reheat  one  gallon  of 
water,  or  to  supply  one  square  foot  of  heating  surface  one 
hour  at  an  outside  temperature  of  zero  degrees.  Take  the 
average  temperature  for  the  seven  cold  months  at  32  de- 
grees. This  is  the  average  for  the  co'ldest  year  in  the  twenty 
years  preceding  1910,  as  recorded  at  the  U.  S.  Exp.  Station, 
LaFayette,  Indiana.  We  then  have  an  average  difference 
between  the  inside  and  the  outside  temperatures  in  any 
residence  of  70  —  32  =  38.  This  makes  the  formula  for 
the  heat  loss,  Art.  28,  reduce  to  38  -7-  70  =  .54  of  its  former 
value.  Now,  if  it  takes  one  gallon  of  water  per  square  foot 
of  radiation  per  hour  under  maximum  conditions,  we  have 
for  the  seven  months  .54  X  7  X  30  X  24  =  2722  gallons  of 
water  needed  for  each  square  foot  of  radiatk>n  per  each 
heating  year.  This  is  equivalent  to  2722  X  .0027  =  7.35  cents 
per  square  foot  of  radiation  for  the  heating  year  of  seven 
months. 

When  the  plant  is  working  under  the  best  conditions 
this  figure  can  be  reduced.  It  can  be  done  with  boilers 
of  a  higher  efficiency  than  that 'stated,  or  by  using  a  cheaper 
coal,  both  of  which  are  possible  in  many  cases. 

172.  Cost  of  Heating  from  a  Central  Station.  Summary 
of  -Tests: — The  following  tests  were  conducted  upon  the 
Merchants  Heating  and  Lighting  Plant,  LaFayette,  Ind. ;  one 
in  1906  and  the  other  in  1908.  The  plant  was  changed  slight- 
ly between  the  two  tests  and  'the  radiation  carried  upon  the 
lines  was  much  increased,  although  in  all  essential  features 
the  plant  was  the  .same.  The  circulating  water  was  heated 
by  exhaust  steam  heaters  and  by  heating  boilers. 

The  plant  had  the  following  important  pieces  of  appara- 
tus employed  in  generating  or  absorbing  the  heat  supply: 

BOILERS    (Steaming  a,nd   Heating). 

Two  125  H.  P.  Stirling  boilers.  Total  heating  surface 
2524  sq.  ft. 

Three  250  H.  P.  Stirling  boilers.  Total  heating  surface 
7572  sq.  ft. 

Pressure  on  steam  boilers  (gage),  150  Ibs. 

Pressure  on  heating  boilers   (approx.),  60  Ibs. 


DISTRICT   HEATING  261 

ENGINES. 

One  450  H.  P.  Hamilton  Corliss  comp.  engine,  direct  con- 
nected to  a  300  K.  W.  Western  Electric  72-pole  alternating 
current  generator  120  R.  P.  M.  This  engine  carried  the  load 
of  the  plant  when  it  was  above  50  K.  W.,  which  was  generally 
from  5:30  A.  M.  to  11:30  P.  M.  When  this  unit  was  run,  direct 
current  was  obtained  by  passing  the  alternating  current 
through  a  motor  generator  set. 

One  125  H.  P.  Westinghouse  comp.  engine,  belted  to  one 
75  K.  W.  3-phase  alternating  and  two  direct  current  genera- 
tors, and  run  at  312  R.  P.  M.  This  unit  was  generally  run 
between  11:30  P.  M.  .and  5:30  A.  M. 

One  250  H.  P.  Westinghouse  comp.  engine,  belt  connected 
to  a  200  K.  W.  generator  and  two  smaller  machines. 

PUMPS. 

.;-••  •  *• 

One  centrifugal,  two-stage  pump,  Dayton  Hydraulic  Co., 
direct  connected  to  a  Bates  vertical  high  speed  engine  at  300 
R.  P.  M. 

Two  Smith-Vaile  horizontal  recip.  duplex  pumps  14  in. 
X  12  in.  X  18  in.  Each  of  the  three  pumps  connected  to  the 
return  main  in  such  a  way  as  to  be  able  to  use  any  combina- 
tion at  any  one  time  to  circulate' the  water.  The  centrifugal 
pump  had  been  in  service  only  one  season.  It  had  a  capacity 
about  equal  to  the  two  reciprocating  pumps  and  under  the 
heaviest  service  this  pump  and  one  of  the  duplex  pumps 
1  were  run  in  parallel. 

One  Smith-Vaile  horizontal  reciprocating  tank  pump 
6  in.  X  4  in.  X  6  in.  to  lift  the  water  of  condensation  from 
the  exhaust  heater  to  the  tank. 

One  Smith-Vaile  horizontal  reciprocating  make-up  pump 
6  in.  X  4  in.  X  6  in.  to  replace  the  water  that  was  lost  from 
the  system. 

Two  National  horizontal  reciprocating  boiler  feed  pumps. 

One  91/&  in.  Westinghouse  air  pump,  to  keep  up  the  sup- 
ply of  air  through  the  conduits  to  the  regulator  system  in 
the  heated  buildings. 

One  Deane  vertical  deep  well  pump,  to  deliver  fresh 
water  to  the  .supply  tank. 

One  Baragwanath  exhaust  steam  heater  or  condenser, 
having  1000  sq.  ft.  of  heating  surface. 


262 


HEATING   AND   VENTILATION 


PARTIAL   SUMMARY    OF    RESULTS. 

1906  1908 

1.  Square  feet  of  radiation 118000  150000 

2.  Temperature    of   circulating   water   in 

degrees  FM  flow  main 158.36         164.4 

3.  Temperature   of   circulating  water  in 

degrees  F.,  return  main 139.9  139.6 

4.  Temperature    of  circulating  water  in 

degrees  F.,  after  leaving  heater 145.6  147. 

5.  Temperature    of    outside    air    in    de- 
grees F.   32.6  37.5 

6.  Temperature    of    stack    gases    in    de- 
grees F.,  steaming  boiler 566 . 8 

7.  Temperature    of    stack    gases    in.   de- 
grees F.,  heating  boiler 562.  656. 

8.  Draft   in   stacks  (all  boiilers  averaged) 

in  inches  of  water .  689  . 595 

9.  Heating    value    of    coal    in    B.    t.    u. 

per  pound    12800  11565 

10.  B.   t.   u.    delivered   to   steaming   boiler 

per  hour  by  ooal   18187000       25833000 

11.  B.    t.    u.    delivered   to    heating   boilers 

per  hour  by  coal 19226000       27917000 

12.  B.  t.  u.  delivered  to  circulating  water 

by  heating  boilers  per  hour 11800000       15405000 

13.  B.  t.  u.  to  be  charged  to  heating  boil- 
ers (Item  12 — Item  15) 7650000          6934000 

14.  B.  t.  u.  delivered  to  circulating  water 
by    exhaust    'steam    from    the    gener- 
ating engines  per  hour   3600000          6602000 

15.  B.     t.     u.     thrown    away    during     test 
from    pump    exhausts    and    available 

for  heating  circulating  water 4150000          8471000 

16.  B.    t.    u.    available    for   heating    circu- 
lating water  from  all   exhaust  steam 
as    in    normal    running    (Item    14    + 

Item  15)    7750000        15073000 

17.  Total    B.    t.    u.    given    to    circulating 

water  per  hour  (Item  13  +  Item  16).  .15400000       22007000 

18.  Gallons    of    water    pumped    per    hour 

[Item  17  -r-  (8.33  X  Items  2— 3)] 100000  108000 


DISTRICT   HEATING  263 

19.  Gallons   of  water  pumped  per  square 
foot   of  'radiation   per   hour    (Item    18 

-T- Item  1)   .85  .70 

20.  Efficiency    of    heating    boilers     (Item 

12  -T-  Item  11)  approx .  .60  .55 

21.  Value  of  the  coal  in  cents  per  ton  of 

2000  pounds  at  the  plant   200.  175. 

22.  Average  electrical  horse-power 68  141 

'Note. — The   above  values   are  averages  and   were   taken 

for   each   entire    test.      The   B.    t.    u.    values   were   co-nsidered 
satisfactory  when  approximated  to  the  nearest  thousand. 

173.  Regulation: — The  regulation  of  the  heat  within  the 
residences  is  best  controlled  from  the  power  plant.  In.  most 
heating  plants  a  schedule  is  posted  at  the  power  house  which 
tells  the  engineer  the  necessary  temperature  of  the  circu- 
lating water  to  keep  the  interior  of  the  residences  at  70 
degrees  with  any  given  outside  temperature.  The  Merchants 
Heating  and  Lighting  Company  mentioned  above  use  the 
following  schedule: 


Atmosphere 
i60  deg. 
50     " 

Water 
120  deg. 
140     " 

Atmosphere 
10  deg. 

0     " 

Water 
190  deg. 
200  " 

40     " 

150     " 

—10     " 

210  " 

30     " 

160     " 

—20     " 

220  " 

20     " 

180     " 

In  addition,  read  the  article  by  Mr.  G.  E.  Chapman,  pub- 
lished in  the  Heating  and  Ventilating  Magazine,  August 
1912,  page  23,  in  which  he  describes  the  methods  used  in 
regulating  the  Oak  Park,  111.  plant. 

In  some  heating  plants  the  regulation  is  by  means  of  air 
carried  from  the  compressor  at  the  power  house  through  a 
main  running  parallel  with  the  water  mains  in  the  conduits 
and  branching  'to  each  building  where  it  is  used  under  a 
pressure  of  15  pounds  to  operate  thermostats,  which  in  turn 
control  the  water  imlebs  to  'the  radiators.  A  closer  regula- 
tion is  obtained  in  the  latter  .system  'than  in  the  former,  but 
if  is  needless  to  say  that  the  thermostats  require  careful 
adjustments  and  frequent  inspections. 

Diaphragms  or  chokes  having  different  .sized  orifices  may 
be  placed  on  the  return  main  from  each  building  to  negulate 
the  supply.  Those  buildings  nearest  to  the  power  plant 
have  the  advantage  of  a  greater  differential  pressure  than 


264  KEATING  AND  VENTILATION 

those  farther  away,  hence  should  have  smaller  diaphragms. 
By  increasing  the  resistance  in  the  return  line  from  any 
buildiing  the  water  circulates  more  slowly  and  has  time  to 
give  off  more  heat  to  the  rooms.  With  a  high  temperature 
of  the  water  and  a  careful  adjustment  of  the  diaphragms 
it  is  possible  to  have  the  amount  of  water  circulated  per 
square  foot  of  radiation  reduced  much  below  one  gallon  per 
square  foot  per  hour. 

STEAM  SYSTEMS. 

174.  Heating  by  steam  from  a  central  station,  compared 
with  hot  water  heating,  is  a  very  sample  process.  The  power 
plant  equipment  is  composed  of  a  few  inexpensive  parts,  the 
operation  of  which  is  very  simple  and  easily  explained. 
These  parts  have  but  few  points  that  require  rational  de- 
sign. Because  of  the  simplicity  and  the  similarity  to  the 
preceding  discussion  on  hat  water  systems,  the  work  on 
steam  systems  will  be  very  brief.  All  questions  referring 
to  the  construction  of  the  conduit,  the  supporting  of  the 
pipes,  the  provision  for  contraction  and  expansion,  the  drain- 
fing  of  the  pipes  amd  conduits,  are  common  to  both  hot 
water  and  steam  systems  and  are  discussed  in  Arts.  138  and 
139.  A  large  part  of  the  work  referring  directly  to  district 
hot  water  heating  applies  with  almost  equal  force  to  steam 
heating.  This  part  of  the  work,  therefore,  will  deal  with 
such  parts  of  the  power  plant  equipment  as  differ  from 
those  of  the  hot  water  system. 

Steam  heating  may  be  classified  under  two  general 
heads,  high  pressure  and  low  pressure.  A  very  small  part 
of  the  heating  in  this  country  is  now  done  by  what  may  be 
strictly  called  higih  pressure  service,  i.  e.,  where  radiators  or 
ooils  are  under  pressures  from  30  to  60  pounds  gage,  and 
this  small  amount  is  gradually  decreasing.  Ordiinanily, 
steam  is  generated  at  high  pressure  at  the  boiler,  60  pounds 
to  150  pounds  gage,  and  reduced  for  line  service  to  pressures 
varying  from  0  to  30  pounds  gage,  with  a  still  further  re- 
duction at  the  building  to  pressures  varying  from  0  to  10 
pounds  gage,  for  use  in  radiators  and  ooils.  Where  exhaust 
steam  is  used  in  the  main,  the  pressure  is  not  permitted  to 
go  higher  than  10  pounds  gage,  because  of  the  back  pres- 
sure on  the  engine  piston.  Where  exhaust  steam  i-s  not 
used,  the  pressures  may  go  as  high  as  30  pounds  gage,  thus 
allowing  for  a  greater  pressure  drop  in  the  line  and  a  corre- 


DISTRICT   HEATING 


265 


spending  reduction  in  pipe  sizes.  Vacuum  returns  may  be  ap- 
plied to  central  station  work  the  same  as  to  isolated  plants. 
The  principles  involved  in  the  power  plant  end  of  a 
staa<m  heating  system  may  be  represented  by  Fig.  119.  It 
will  be  seen  that  the  exhaust  steam  from  the  engines  or  tur- 
bines has  four  possible  outlets.  Passing  through  the  oil 
separator,  which  removes  a  large  part  -of  the  entrained  oil, 
part  of  the  exhaust  steam  is  turned  into  the  heater  for  use  in 
heating  the  boiler  feed  water.  The  rest  of  the  steam  passes 
on  into  the  heating  system.  If  there  be  more  exhaust  steam 
than  is  necessary  to  supply  the  heating  system,  the  balance 
may  go  to  the  atmosphere  through  the  back  pressure  valve. 
When  the  heating  system  is  not  in  use,  as  would  be  the  case 
in  the  four  warm  months  of  the  year,  the  exhaust  isteam  may 
be  passed  into  the  condenser. 


3YPA5S  AROUND  HEATER 

ro  BACKPRESSURE  VALVE 


PAR A TOR 


TO HEATER  AND 
BACK  PRESS  VALVE 


7DCOKDEINSCR 


LIVE  3TETAM 
FROM  BOILERS 


Fig.   119. 


It  is  very  evident,  from  what  has  been  said  before,  that 
it  would  not  be  economical  to  condense  the  steam  in  a 
condenser  as  long  as  there  is  a  possibility  of  using  it  in  the 
heating  system.  The  increased  gain  in  efficiency,  when  con- 
densing the  exhaust  steam  under  vacuum,  is  very  ismall  com- 
pared to  the  gain  when  'this  same  steam  is  used  for  heating 
purposes.  It  would  be  also  very  poor  eooinomy  to  use  any 
live  steam  for  heating  when  there  were  'any  exhaust  steam 
wasted.  When  the  amount  of  exhaust  isteam  :is  d  insufficient, 
live  steam  is  admitted  through  a  pressure  reducing  valve. 

175.  Drop  In  Pressure  and  the  Diameter  of  the  Mains:— 
The  flow  of  steam  in  a  pipe  follows  the  same  general  law  as 


266  HEATING  AND  VENTILATION 

the  flow  of  water.  The  loss  of  head  may  be  represented 
by  the  well  known  formula 

261V2 

111  = (101) 

Od 

wliere  Tif  =  loss  of  head  in  feet,  <f>  =  coefficient  of  friction, 
v  =  velocity  in  feet  per  second,  I  =  length  of  pipe  in  feet, 
d  =  ddametar  of  the  pipe  in  feet  and  g  =  32.2.  Substitute, 
Jif  =  144  p  -+•  D,  wliere  p  =  drop  in  pressure  in  pounds  and 
D  =  density  of  the  steam,  and  find 

2  <£  I  v2  D 

p  =  (102) 

144  gd 

The  coefficient  of  friction  is  found  to  vary  wlith  the  velocity 
•of  the  steam  and  with  the  diameter  of  the  pipe.  Prof.  Unwin 
found  that  for  velocities  of  100  feet  per  second  (good  prac- 
tice for  transmission  lines),  it  could  be  expressed  as  follows, 
where  c  is  a  constant  to  be  found  by  experiment, 


10  d 

which,  when  substituted  in  formula  102,  gives 
lv2Dc 


(103) 
10  d     ' 

Let  TF  =  pounds  of  steam  passing  ptr  minute  and  <7i  =  diam- 
eter of  pipe  in  inches,  then 

1            /             3.6    \      W2lc 
P  =  ——         1+  — —  d04) 


20.663 

From  this  formula  we  may  obtain  any  one  of  the  three  terms, 
W,  di  or  p,  if  the  other  two  are  known.  Table  36,  Appendix, 
was  compiled  from  formula  104  with  c  =  .0027.  For  discus- 
sion, see  Trans.  A.  S.  M.  E.,  Vol.  XX,  page  342,  by  Prof.  R.  C. 
Carpenter.  Also  Encyclopedia  Britannica,  Vol.  XII,  page  491. 
See  also,  Kent,  page  670,  and  Carpenter's  H.  &  V.  B.,  page  51. 
It  will  be  seen  that  Table  36  is  compiled  upon  the  basis 
of  one  pound  pressure  drop,  at  an  average  pressure  of  100 
pounds  absolute  in  the  pipe.  Since  in  any  case  the  drop 
in  pressure  is  proportional  to  the  square  of  the  pounds  of 
steam  delivered  per  minute  (other  terms  iremiaining  con. 
stant),  the  amount  delivered  at  any  other  pressure  drop 
than  that  given  (one  pound)  would  be  found  by  multiplying 


DISTRICT   HEATING  26? 

the  amount  given  in  the  table  by  the  square  root  of  the 
desired  pressure  drop  in  pounds.  Also,  since  the  weight  of 
steam  moved  at  the  same  velocity,  under  any  other  absolute 
pressure,  is  approximately  proportional  to  the  absolute  pres- 
sures (other  terms  remaining1  constant),  -  we  'have  the 
amount  of  steam  moved  under  the  given  pressure,  found  by 
multiplying  the  -amount  given  in  the  table  by  the  square 
root  of  <the  'ratio  of  the  absolute  pressures.  To  illustrate  the 
use  of  the  table — suppose  the  pressure  drop  in  a  1000  foot 
run  of  6  linch  pipe  is  8  ounces,  when  the  average  pressure 
within  the  pipe  is  10  pounds  gage.  Th£  amount  <of  steam 
carried  per  minute  is  93.7  X  V.lf-r-  V100  •*•  25  =  33  pounds. 
Or,  if  the  drop  is  4  pounds,  at  an  -average  inside  pressure  of 
50  pounds  gage,  the  amount  carried  would  be  150  pounds 
per  minute.  Conversely — find  t-he  diameter  of  a  pipe,  1000 
feet  long,  'to  carry  150  pounds  of  steam  per  minute,  at  an 
average  pressure  of  50  pounds  gage  and  a  pressure  drop  of 
8  ounces. 


150              /100 
W  (table)  = —  X  J =  264  pounds 

V. 


150  1100 

=  —  X   \ = 

V.5  \    65 

which,  according  to  the  table,  gives  a  9  inch  pipe. 

176.  Dripping  the    Condensation    from   the    Mains: — The 

condensation  of  the  -steam,  which  takes  place  in  the  con- 
duit mains,  should  be  dripped  to  the  sewer  oir  the  return 
at  certain  specified  points,  through  some  form  of  steam 
trap.  These  traps  should  be  kept  in  first  class  condition. 
They  should  be  inspected  every  seven  or  ten  days.  No  pipe 
should  be  drilled  and  tapped  for  this  water  drip.  The  only 
satisfactory  way  is  to  cut  the  pipe  and  insert  a  tee  with 
the  branch  Looking  downward  and  leading  to  the  trap.  The 
sizes  of  the  traps  and  the  distances  between  them  can  only 
be  determined  when  the  pounds  of  condensation  per  running 
foot  of  pipe  can  be  estimated. 

177.  Adaptation     to     Private     Plants: — District     steam 
heating  systems  may  be  adapted  to  private  hot  water  plants 
by  the  use  -of  a   "transformer."     This   in  principle  is  a   hot 
water  tube  heater  which  takes  'the  place  >of  the  hiot   water 
heater  of  the  system.     It  may  also  be  adapted  to  warm  air 
systems    by    putting  the    steam    through    indirect    coils   and 
taking  the  air  supply  from  over  the  coils. 


268  HEATING  AND   VENTILATION 

178.      General   Application    of   the   Typical    Design: — The 

following  brief  applications  are  meant  to  be  suggestive  of 
the  method  only,  and  the  discussions  of  the  various  points 
are  omitted. 

Square  feet  of  radiation  in  the  district. — 

R*  =  184500  X  170  -f-  255  =  123000  square  feet. 

Amount  of  heat  needed  in  the  district  to  supply  the  radiation  for 
one  hour  in  zero  weather. — 

Total  heat  per  hour  =  123000  X  255  =  31365000  B.  t.  u. 

Amount  of  heat  necessary  at  the  power  plant  to  supply  the  radia- 
tion -for  one  hour  in  zero  weather. — Assuming  15  per  cent,  heat 
loss  in  the  conduit  (this  is  slightly  less  than  that  allowed  for 
the  hot  water  two-pipe  system,  20  per  cent.),  we  have 
31365000  -T-  .85  =  36900000  B.  t.  u.  per  hour. 

Total  exhaust  steam  available  for  heating  purposes. — 
W*  (max.)  =  (23100  +  8680)  X  1.15  =  36547  pounds  per  hour. 
TF«  (min.)  =  (   1490  +  8680)   X  1.15  =  11696  pounds  per  hour. 

Total  B.  t.  u.  available  from  exhaust  steam  per  hour  for  heating.— 
Let  'the  average  pressure  in  the  line  be  5  pounds  gage  and 
let  the  water  of  condensation  leave  the  indirect  coils  in  the 
residences  at  140  degrees.  We  then  have  from  one  pound  of 
exhaust  steam,  by  formula  72, 

B.  t.  u.  =  .85  X  960  +  195.6  —  (140  —  32)  =  903.7 
Assuming  this  to  be  900  B.  t.  u.  per  pound,  the  total  available 
heat  from  the  exhaust  steam  for  use  in  the  heating  system 
is,  maximum  total  =  32892300  B.  t.  u.  and  the  minimum  total, 
=  10526400  B.  t.  u. 

Square  feet  of  steam  radiation  that  can  he  supplied  by  one  pound 
of  exhaust  steam  at  5  pounds  gage. — 

R,  =  900  -r-  (255  -r-  .85)  =  3. 

Total  B.  t.  u.  to  be  supplied  by  live  steam. — 

B.  t.  u.  (max.  load)  =  36900000  —  32892300  =  4007700  B.  t.  u. 
B.  t.  u.  (min.  load)  =  36900000  —  10526400  =  26373600  B.  t.  u. 

Total  pounds  of  live  steam  necessary  to  supplement  the  exhaust 
steam. — Let  the  steam  be  generated  in  the  boiler  at  125 
pounds  gage.  With  feed  water  at  60  degrees 

Max.  load  =     4007700  -r-  1163.8  =     3444  pounds. 

Min.  load  =  26373600  -f-  1163.8  —  22661  pounds. 


DISTRICT    HEATING 


269 


Boiler  horse-power  needed  for  the  steam  power  units. — As  in 
Arts.  167  and  170, 

Bs.  H.  P.   (max.)  =  36547   X  1.2  -r-  34.5  =  1271. 
Bs.  II.  P.  (min.)    =  11696  X  1.2  -f-  34.5  =     407. 

Total  hotter  horse-power  needed  in  the  plant. — Maximum  load. 
B.  //.  P.  (total)  =  1271  +  (3444  X  1.2  -J-  34.5)  =  1391. 

It  will  be  noticed  that  this  total  horse-power  is  157 
horse-power  less  than  the  corresponding  Case  2  in  Art.  170. 
This  is  accounted  fo-r  by  the  fact  that  no  steam  is  used  up  in 
work  dn  the  circulating  pumps,  als'o  'that  the  conditions  of 
steam  generation  and  circulation  are  slightly  different.  1500 
boiler  horse-power  would  probably  be  installed  in  this  case. 

Size  of  conduit  mains. — Let  it  be  required  to  find  the 
diameters  of  -the  main  system  In  Fig.  115  at  the  important 
points  shown.  Art.  147  gives  the  length  of  the  mains  in  each 
part.  Allow  .3  pound  of  steam  far  each  square  foot  >of  steam 
radiation  per  hour  ('this  will  no  doubt  be  .sufficient  to  supply 
the  radiation  -and  conduit  losses).  Try  first,  'that  part  of  the 
line  between  the  power  plant  and  A,  with  an  average  .steam 
pressure  in  the  lines  of  about  5  pounds  gage  -and  a  drop  in 
pressure  of  IVz  ounces  per  each  100  feet  of  run  (approxi- 
mately 5  pounds  per  mile).  25200  pounds  per  h/our  gives 
W  =  420.  The  length  of  -this  part  of  the  line  -is  200  feet  and 
the  drop  is  3  ounces,  or  .19  pound. 

420  /  100 

W  (table)  =  — —  £/X.   !\t —  2158  pounds 

V.19  \    20 

which  gives  a  15  inch  pipe. 

Following  out  the  same  reasoning  for  all  parts  of  the 
line,  we  have 

TABLE   XXVIII. 

IF  P  to  A  |  A  to  B    |  B  to  C   |  C  to  D    |  D  to  E_ 


Distance  between  points  

200 

500 

1500 

1500 

500 

Radiation   supplied,  sq.   ft  

84000 

57000 

34000 

19000 

8000 

Pressure-drop  in  pounds  —  p  

19 

47 

1  4 

1.4 

.47 

Diameter  of  pipe  in  inches,  by  table... 

15 

13 

11 

9 

5 

In  general  practice,  these  values  would  probably  be 
taken  16,  14,  12,  10  and  6  inches  respectively.  Look  up 
Table  36,  Appendix,  and  check  the  above  figures. 


270  HEATING   AND    VENTILATION 

REFERENCES. 
References    on    District    Heating. 

TECHNICAL  BOOKS. 

Allen,  Notes  on  Heating  and  Ventilation,   p.   131. 
Gifford,  Central  Station  Heating. 

TECHNICAL   PERIODICALS. 

Engineering  News.  Comparison  of  Costs  of  Forced-Circula- 
tion Hot  Water  and  Vacuum-Steam  Central  Heating  Plants, 
J.  T.  Magudre,  Dec.  23,  1909,  p.  692.  Design  of  Central  Hot- 
Water  System  with  Forced-Circulation,  J.  T.  Maguire,  Sept. 
2,  1909,  p.  247.  Engineering  Review.  Determining  Depreciation 
of  Underground  Heating  Pipes,  W.  A.  Knight,  Jan.  1910, 
p.  85.  Some  Remarks  on  District  Steam  Heating,  W.  J.  Kline, 
April  1910,  p.  61.  Toledo  Yaryan  System,  A.  C.  Rogers,  May 
1910,  p.  58.  Some  of  the  Factors  that  Affect  the  Cost  of 
Generating  and  Distributing  Steam  for  Heating,  C.  R.  Bishop, 
Aug.  1910,  p.  56.  Central  Station  Heating  Plant  at  Craw- 
fordsville,  Ind.,  B.  T.  Gifford,  Dec.  1909,  p.  42.  Wilkesbarre 
Heat,  Light  and  Motor  Co.,  A  Live  Steam  Heating  Plant, 
J.  A.  White,  July  1908,  p.  32.  The  Heating  and  Ventilating 
Magazine.  Scho-tt  Systems  of  Central  Station  Heating,  J.  C. 
Hornung,  Nov.  1908,  p.  19.  Data  on  Central  Heating  Sta- 
tions, Nov.  1909,  p.  7.  Cost  of  Heat  from  Central  Plants, 
March  1909,  p.  31.  Steam  Heating  in  Connection  with  Cen- 
tral Stations,  Paul  Mueller,  Oct.  1909,  p.  24;  Nov.  1909,  p.  1. 
A  Modern  Central  Hot  Wlater  Heating  Station,  W.  A.  Wolls, 
July  1910,  p.  15.  Central  Station  Heating,  F.  H.  Stevens,  June 
1910,  p.  5.  The  Profitable  Operation  of  a  Central  Heat- 
ing Station  without  the  Assistance  of  Electrical  or  Other 
Industries,  Byron  T.  Gifford,  Aug.  1910.  Central  Station 
Heating,  Byron  T.  Gifford,  Apr.  1911.  Central  Power  and 
Heating  Plant  for  a  Group  of  School  Buildings,  May  1910. 
Domestic  Engineering.  Report  of  Second  Annual  Conven- 
tion of  the  National  District  Heating  Association  at 
Toledo.  O.,  June  1,  1910.  Vol.  51,  No.  11,  June  11,  1910,  p.  255. 
The  Metal  Worker.  Central  District  Steam  Heating  from 
Hill  Top,  Jan.  15,  1910,  p.  78.  Central  Heating  at  Crawfords- 
ville,  Ind.,  July  30,  1910,  p.  135.  Data  of  77  Central  Station 
Heating  Plants,  Sept.  4,  1909,  p.  48.  Hot  Water  Heating, 
Teupitz,  Germany,  Sept.  25,  1909,  p.  45.  High  Pressure 
Steam  Distribution,  Munich,  Germany,  Oct.  2,  1909,  p.  48. 
Central  Plant  Solely  for  Residence  Oct.  16,  1909,  p.  50. 
Two  Types  of  Central  Heating  Plant  Compared,  Apr.  9,  1910. 
Central  Heating  at  Crawfordsville,  Indiana,  July  30,  1910. 
The  Engineering  Record.  District  Heatdng,  July  15,  1905.  Econ- 
omies Obtainable  by  Various  Uses  of  Steam  in  a  Combined 
Power  and  Heating  Plant,  Feb.  18,  1905.  A  Study  for  a 
Central  Power  and  Heating  Plant  at  Washington,  Feb.  11, 
1905.  Utilization  of  Vapor  of  Steam  Heating  Returns,  Oct. 
22,  1904.  A  Central  Heating,  Lighting  and  Ice-Making  Sta- 
tion, Gulfport,  Miss.,  Feb.  27,  1904.  Purdue  University  Cen- 
tral Heating  and  Po-wer  Station,  Jan.  30,  1904.  A  Central 
Hot-Water  Heating  Plant  in  the  Boston  Navy  Yard,  July 
16,  1904.  Power.  Combined  Central  Heating  and  Electric 
Plants,  Edwin  D.  Dreyfus,  Aug.  20.  1912. 


CHAPTER  XIV. 


TEMPERATURE    CONTROL,    IN    HEATING    SYSTEMS. 


170.  From  testa  that  have  been  conducted  on  heating 
systems,  it  has  been  shown  that  there  is  less  loss  of  heat 
from  buildings  supplied  by  automatic  temperature  control, 
than  from  buildings  where  there  is  no  such  control.  A  uni- 
form temperature  within  the  building  is  desirable  from  all 
points  of  view.  Whe-re  heating  systems  are  operated,  even 
under  the  best  conditioin.s,  without  such  control,  the  effi- 
ciency of  the  system  would  be  increased  by  its  application. 
No  definite  statement  can  be  made  for  -the  amount  -of  heat 
saved,  but  it  is  safe  to  say  that  it  is  between  5  and  20  per 
cent.  A  building  uniformly  heated  during  the  entire  time, 
requires  less  heat  than  if  a  certain  part  or  all  of  the  build- 
ing were  occasionally  allowed  to  cool  off.  When  a  building 
falls  below  normal  temperature  it  requires  an  extra  amount 
of  heat  to  bring  it  up  to  normal,  and  when  the  inside  tem- 
perature rises  above  the  normal,  it  is  usually  lowered  by 
opening  windows  and  doors  to  enable  the  heat  to  leave  rap- 
idly. High  inside  temperatures  also  cause  a  correspondingly 
increased  radiation  loss.  Fluctuations  of  temperature,  there- 
fore, are  not  only  undesirable  for  the  occupants,  but  they 
are  very  expensive  as  well. 

180.  Principles  of  the  System: — Temperature  control  may 
be  divided  into  two  general  classifications, — small  plants 
and  large  plants.  The  control  for  small  plants,  i.  e.,  such  plants 
as  contain  very  few  heating  units*  is  accomplished  by  regu- 
lating the  drafts  by  special  dampers  at  the  combustion 
chamber.  This  method  controls  merely  the  process  of  com- 
bustion and  has  no  especial  connection  with  individual  reg- 
isters or  radiators,  it  being  assumed  that  a  rise  or  fall  of 
temperature  in  one  room  is  followed  by  a  corresponding 
effect  in  all  the  other  rooms.  This  method  assumes  that  all 
the  heating  units  are  very  accurately  proportioned  to  the 
respective  rooms.  The  dampers  are  operated  through  a  sys- 
tem of  levers,  which  system  in  turn  is  controlled  by  a  ther- 
mostat. Fig.  120  shows  a  typical  application  of  such  regu- 


272 


HEATING  AND   VENTILATION 


lation.  This  may  be  ap- 
plied to  any  system  of 
heat.  In  addition  to  the 
thermostatic  control 
from  the  room  to  the 
damper,  as  has  just  been 
mentioned,  closed  hot 
water,  steam  and  vapor 
systems  should  have 
•regulation  from  the 
pressure  within  the 
boiler  to  the  draft.  Oc- 
casionally in  the  miorn- 
i  n  g  the  pressure  in 
either  system  may  be- 
come excessive  before 
the  house  is  heated 

_,  enough   for  the  thermo- 

stat  to   act.      With   such 

additional  .regulation  no  hot  water  heater  or  steam  boiler 
would  be  forced  to  a  dangerous  pressure.  Fig.  121  shows  a 
thermostat  manufactured  by  the  Andrews  Heating  Co.,  Min- 
neapolis. The  complete  regulator  has  in  addi- 
tion to  this,  two  cells  of  open  circuit  batttery 
and  a  motor  box,  all  of  which  illustrate  very 
well  the  thermostatic  damper  control. 

The  thermostat  'Operates  by  a  differential 
expansion  of  the  two  different  metals  com- 
posing the  spring  at  the  top.  Any  change  in 
temperature  causes  one  of  the  metals  to  ex- 
pand or  contract  more  rapidly  than  the  other 
and  gives  a  vibrating  movement  to  the  project- 
ing arm.  This  is  connected  with  the  batteries 
and  with  the  motor  in  such  a  way  that  when 
the  pointer  closes  the  contact  with  either  one 
of  the  contact  posts,  a  pair  of  magnets  in  the 
motor  causes  a  crank  e,rm  to  rotate  through 
180  degrees.  A  flexible  connection  between  this 
crank  and  the  damper  causes  the  damper  to 
open  or  close.  A  change  in  temperature  in 
the  opposite  direction  makes  contact  with  the  other  post 
and  reverses  the  movement  of  the  crank  and  damper.  The 
movement  of  the  arm  between  the  contacts  is  very  small  thus 


TEMPERATURE    CONTROL. 


273 


making1  the  thermostat  very  sensitive.     No  work  is  required 
of  the   battery   except  that   necessary   to   release   the   motor. 

Occasionally  it  is  desira- 
able  to  connect  small  heat- 
ing plants  having-  only  one 
thermostat  in  control,  to  a 
central  station  system.  Fig. 
122  shows  how  the  supply 
of  heat  may  be  controlled 
by  the  above  method. 

Fig.  123  sh'ows  the  Syl- 
phon  Damper  Regulator 
made  by  The  American 
Radiator  Co.,  and  applies 
to  steam  pressure  control. 
The  longitudinal  expansion 
of  a  corrugated  brass  or 
copper  cylinder  operates 
the  damper  through  a  sys- 
tem of  levers.  The  longitu- 
dinal movement  of  the  cyl- 
inder is  small  and  hence 
the  bending  of  the  metal 
in  the  walls  of  the  cylinder 


is   very   slight. 
movement      is 


This   small 
multiplied 


Fig.  122, 


Fig:  123. 


274 


HEATING  AND  VENTILATION 


through  the  system  of  levers  to  the  full  amount  necessary 
to  operate  the  damper.  A  similar  device  is  made  by  the 
same  company  for  application  to  hot  water  heaters. 

Temperature  control  in  large  plants,  i.  e.,  'those  plants  having 
a  large  number  of  heating  units,  is  much  more  complicated. 
In  furnace  systems  this  is  very  much  the  same  as  described 
under  small  plants,  with  additional  dampers  placed  in  the 
air  lines.  The  following  discussions,  therefore,  will  apply 
to  hot  water  and  steam  systems,  and  will  be  additional  to  the 
control  at  the  heater  and  boiler  as  discussed  under  small 
plants.  Fig.  124  shows  a  typical  layout  of  such  a  system. 
Compressed  air  at  15  pounds  per  square  inch  gage  is  main- 
tained  in  cylinder,  Su,  winch  is  located  in  .some  convenient 


Fig.  125. 


Fig.  124 


place  for  the  attendant.  This  air  is  car- 
ried to  the  thermostat,  Th,  on  one  of  the 
protected  walls  in  the  'room.  Here  it 
passes  through  a  controlling  valve  and 
is  then  led  to  the  regulating  valve  on  the 
iradiator.  This  adr  acts  on  the  top  of  a 
rubber  diaphragm  as  shown  in  Fig.  125 
to  close  the  valve  and  to  cut  off  the  sup- 
ply. W.hen  the  room  cools  off,  the  con- 
trolling valve  at  Th  cubs  off  the  supply 
and  opens  the  air  line  to  the  radiator. 
This  removes  the  air  pressure  above  the 


TEMPERATURE    CONTROL  275 

diaphragm  and  permits  the  stem  of  the  valve  to  lift.  On  the 
opening  of  the  valve  the  steam  or  water  again  enters  the 
radiator  and  the  cycle  is  completed. 

Fig.  96  shows  the  application  of  the  thermostatic  control 
to  the  blower  work.  This  show,s  the  thermostat  B  and  the 
mixing  dampers,  located  at  the  plenum  chamber,  in  the 
single  duct  system.  The  same  general  arrangement  could 
be  applied  to  the  double  duct  system,  with  the  dampers  in 
the  wall  at  the  base  of  the  vertical  duct  leading  to  the 
room. 

181.  Some  of  the  Important  Points  in  the  Installation: — 

Each  radiator  has  its  own  regulating  valve.  All  rooms 
having  three  radiators  or  less  are  provided  with  one  thermo- 
stat. Large  rooms  having  four  or  more  radiators  have  two  or 
more  thermostats  with  not  more  than  three  radiators  to  the 
thermostat.  Where  other  motive  power  .is  not  available  fo.r 
the  -air  supply,  a  hydraulic  compressor  is  used.  This  com- 
pressor automatically  maintains  the  air  pressure  at  15 
pounds  gage  in  the  steel  supply  tank.  The  main  air  trunk 
lines  are  galvanized  i>ron,  %  and  ^  inch  in  diameter,  and 
are  tested  under  a  pressure  of  25  pounds  gage.  All  branch 
pipes  are  ^  and  %  inch  galvanized  iron.  All  fittings  on 
the  l/a  inch  pipes  are  usually  brass.  W»here  flexible  connec- 
tions are  made,  this  is  sometimes  done  by  armoured  lead 
piping.  Thermostats  are  usually  provided  with  metallic 
covers,  and  are  finished  to  correspond  with  the  hardware  of 
the  respective  rooms.  Each  thermostat  is  provided  with  a 
thermometer  and  a  scale  for  making  adjustments.  Each 
radiator  is  provided  with  a  union  diaphragm  valve  having 
a  specially  prepared  rubber  diaphragm  with  felt  protection. 
This  valve  replaces  the  ordinary  radiator  valve.  One  of 
these  valves  iis  used  on  the  end  of  each  hot  water  radiator, 
one  on  each  one-pipe  steam  radiator  and  two  on  each  two- 
pipe  low  pressure  steam  radiator.  This  lasit  condition  does 
not  hold  for  two-pipe  steam  radiators  with  mechanical 
vacuum  returns,  'in  which  case  patented  specialties  are 
applied  by  the  vacuoim  company.  In  such  cases  the  supply 
to  the  radiator  only  is  controlled.  '  In  any  first  clas,s  system 
of  control,  the  temperature  of  the  room  may  easily  be  kept 
within  a  ma.ximum  fluctuation  of  three  degrees. 

182.  Some  Special  Designs  of  Apparatus: — All  tempera- 
ture control  work  is   solicited  by  specialty  companies,    each 
having  a   patented   system.     In  the   essential   features  these 


276 


HEATING   AND    VENTILATION 


systems  all  agree  with  the  foregoing  general  statements. 
The  chief  difference  is  in  the  principle  upon  which  the  ther- 
mostat, Th,  operates. 


INTERMEDIATE 
A 


E\l 


Fig.   126. 

Fig-.  126  shows  'Section*  through  the  Intermediate  and 
positive  thermostats  manufactured  by  the  Johnson  Service 
Company,  Milwaukee.  The  interior  workings  of  the  ther- 
mostats are  as  follows:  Intermediate. — Air  enters  at  A  from 
the  supply  tank,  passes  into  chamber  B  and  escapes  at  port 
C.  If  thermostatic  -strip  T  expands  inward  to  close  C,  the 
air  pressure  collects  in  B  and  presses  down  port  valve  V, 
thus  opening  port  E,  letting  -air  through  into  F  and  out  at  O 
to  close  the  damper.  When  T  expands-  outward,  pressure  at 
B  is  relieved  and  V  is  forced  back  by  ia  spring,  closing  E. 
Air  in  F  reacts  against  the  diaphragm  and  escapes  through 
holl-ow  valve  V  at  H,  permitting  the  damper  to  open.  Posi- 
tive.— Air  enters  at  A,  passes  into  chamber  B  and  escapes 
at  C.  If  thermostatic  strip  T  expands  inward  to  close  C,  air 
pressure  collects  in  B,  forces  out  the  knuckle  joint  K  and 


TEMPERATURE    CONTROL  277 

operates  the  three-way  valve  V,  thus  shutting  port  E  and 
opening  port  F,  letting  air  escape  and  radiator  valve  open. 
When  T  expands  outward,  pressure  at  B  is  relieved,  knuckle 
joint  A'  returns,  pulling  V  'Outward,  thus  shutting  port  F, 
opening  E,  letting  air  escape  through  O  and  shutting  off 
radiator  valve. 

The  real  thermostat  is  the  spring  T.  This  is  composed 
of  steel  and  brass  strips  brazed  together.  Because  of  a 
higher  coefficient  of  expansion  in  the  brass  than  in  the 
steel,  a  change  in  the  room  temperature  causes  the  spring 
to  move  toward  or  away  from  the  seat  C.  T  is  adjustable 
for  any  desired  room  temperature.  The  intermediate  ther- 
mostat is  used  on  indirect  heating  where  mixing  dampers 
are  employed  and  where  an  intermediate  position  of  the 
valve  is  necessary.  The  positive  thermostat  is  used  on 
direct  radiators  and  coils  where  a  full  open  or  full  closed 
movement  of  the  valve  is  desired. 

Fig.  127  shows  a  section  through  the  pattern  K  thermo- 
stat, manufactured  by  the  Powers  Regulator  Co.,  Chicago. 
This  thermostat  consists  of  a  frame  carrying  two  corrugated 
disks,  brazed  together  at  the  circumference  a/nd  containing  a 
volatile  liquid  having  a  boiling  point  at  about  50.  degrees  P. 
At  a  temperature  of  about  70  degrees,  the  vapor  within 
the  disks  has  a  pressure  of  about  6  pounds  to  the  square 
inch.  This  pressure  varies  with  every  change  of  tempera- 
ture and  produces  variations  in  the  total  thickness  at  the 
center  of  the  disks. 

The  compressed  air  enters  at  B  and  passes  into  chamber 
IV  through  the  controlling  valve  J,  which  is  normally  held  to 
its  seat  by  a  coil  spring  under  cap  P.  Within  the  flange  M 
is  located  an  escape  valve  L  upon  w.hich  the  point  of  the 
supply  valve  J  rests.  Valve  L  tends  to  remain  open  when 
permitted  by  reason  of  the  spring  underneath  the  cap.  Wfhen 
the  temperature  rises  sufficiently  to  cause  the  disks  to  in- 
crease in  thickness  and  move  the  flange  M,  the  ftrst  action 
is  to  seat  the  escape  valve  L,  its  spring  being  weaker  than 
that  above  J.  If  the  expansive  motion  is  continued  after 
valve  L  is  seated,  the  valve  J  is  then  lifted  from  its  seat 
and  compressed  air  flows  into  the  chamber  N.  As  the 
air  accumulates  in  chamber  N,  it  exerts  a  pressure  upon  the 
elastic  diaphragm  K  in  opposition  to  'the  expansive  force  of 
the  disk.  So,  whenever  there  is  sufficient  pressure  in  N  to 
balance  the  power  exerted  by  the  disks,  the  valve  J  returns 


278 


HEATING   AND   VENTILATION 


Fig.  127. 

to  its  seat  and  no  more  air  is  permitted  to  pass  through. 
If  the  temperature  falls,  the  pressure  within  the  disks  be- 
comes less,  the  disks  draw  together  and  the  over-balancing 
air  pressure  in  N  reverses  the  movement  of  the  flange  M  and 
permits  the  escape  valve  L  under  the  influence  of  its  spring 
to  rise  from  its  seat,  whereupon  a  portion  of  the  air  in  N 
is  discharged  until  the  pressure  in  N  becomes  equal  to  the 
diminished  pressure  from  the  disks.  Thus  the  pressure  of 
the  air  in  N  is  maintained  always  in  direct  propOTtion  to  the 
expansive  power  (temperature)  of  the  disks.  Port  7  con- 
nects with  chamber  N  and  leads  to  the  diaphragm  valve. 

This  thermostatic  valve  controls  the  regulator  valve  by 
a  graduated  movement  and  is  used  on  the  dampers  for 
blower  work.  Another  form  with  maximum  movement  only 
is  designed  for  steam  systems. 

Fig.  128  shows  the  positive  and  graduated  thermostats 
as  manufactured  by  the  National  Regulator  Company,  Chi- 
cago. The  thermO'Static  element  in  these  thermostats  is  the 
vulcanized  rubber  tube  A,  which  changes  its  length  with  the 
varying  room  temperatures  and  causes  the  valve  O  to  open 
or  close  the  port  Q,  thus  controlling  the  supply  of  air  to 


TEMPERATURE    CONTROL 
POSITIVE  INTERMEDIATE 


279 


and  from  the  radiator  valve  or  the  regulating  damper.  In 
the  positive  thermostat  air  enters  the  tube  from-  the  supply 
through  the  filter  and  restricted  passage  P.  From  the  in- 
terior of  the  tube  the  air  leaves  through  the  middle  orifice 
a>nd  enters  the  pipe  leading  to  the  radiator  valve.  If  the 
room -temperature  is  above  the  normal,  port  O  closes  and  the 
air  pressure  collects  in  the  tube,  thus  creating  a  pressure 
in  the  line  leading  to  the  radiator  valve  and  closing  it.  If 
the  room  temperature  falls  below  the  normal,  port  G  opens, 
air  is  exhausted  from  the  tube  to  'the  atmosphere,  the  pres- 
sure on  the  radiator  valve  is  released  and  the  valve  opens. 
The  intermediate  thermostat  differs  from  the  positive  ther- 
mostat in  having  but  one  air  line.  Room  temperatures 
below  the  normal  contract  tube  A,  open  port  G,  and  exhaust 
the  air  to  the  atmosphere.  With  this  release  in  pressure  in 
the  pipe  at  P  the  regulating  damper  is  turned  to  admit 
more  warm  air  into  the  Toom.  With  the  room  temperature 
above  the  normal,  tube  A  expands,  port  G  closes,  pressure  in 
pipe  P  increases  and  the  regulating  damper  is  turned  so  as 
to  admit  <a  lower  temperature  of  air  in  the  room.  By  means 
of  this  a  graduated  movement  of  the  damper  is  obtained. 


REFERENCES. 
References  on  Temperature  Control. 

Metal   Worker.      Temperature    Control    in    House    Heating, 
Jan.  7,  1911. 


CHAPTER   XV. 


ELECTRICAL,   HEATING. 


In  the  present  state  of  the  heating  business  it  seems 
almost  unnecessary  to  discuss  electrical  heating,  in  any 
serious  way,  in  connection  with  steam  power  plants.  The 
reasons  will  be  seen  in  the  following  brief  discussion. 
Electrical  heating  can  appeal  to  the  public  only  from  the 
standpoint  of  convenience,  since  a  comparison  of  economies 
between  steam,  hot  water  or  warm  air  heating  on  one  hand, 
and  electrical  heating  on  the  other,  is  wholly  against  the 
latter.  Its  application  to  the  processes  of  heating  will  find 
its  greatest  economy  in  connection  with  water  power  plants 
where  the  combustion  of  fuel  is  eliminated  from  the  prop- 
osition. This  discussion  will  not  bear  in  any  way  upon  the 
water  power  generator. 

183.  Equations  Employed  In  Electrical  Heating:  Design :— 

1  H.  P.  =  746  watts. 

1  H.  P.  =  33000  ft.  Ibs.  per  min.  =  1980000  ft.  Ibs.  per  hr. 

1  B.  t.  u.  =  778  ft.  Ibs. 

1  H.  P.  hr.  =  1980000  -r-  778  =  2545  B.  t.  u.  per  tor. 

1  H.  P.  hr.  =  746  watt  hrs.  =  2545  B.  t.  u.  per  hr. 

a  watt  hr.  =  3.412  B.  t.  u.  per  hr. 

1  watt  hr.  =  3.412  -r-  170  =  .02  sq.  ft.  of  hot  water  rad. 

1  watt  hr.  =  3.412  -h  255  =  .0134  sq.  ft.  of  steam  rad. 

1   kilo-watt  hr.  =  20.1  sq.  ft.  of  hot  water  rad.  (105) 

1  kilo-watt  hr.  =  13.4  sq.  ft.  of  steam  rad.  (106) 

184.  Comparison    between    Electrical   Heating   and   Hot 
"Water  and   Steam   Heating: — The  loss    in  transmitting  elec- 
tricity from  the  generators  through  the  switchboard  to  the 
radiators  may  be  small  or  large,  depending  upon  the  condi- 
tions of  wiring,  the  current  transmitted  and  the  pressure  on 
the   line.      In   all    probability    it    would    equal    or   exceed    the 
transmission  losses  in  hot  water  or  steam  lines.     Assuming 
these  losses  to  be  the  same,  a  fair  comparison  may  be  made 
in  the  cost  of  .heating  by  the  various  -methods.     The  operat- 
ing efficiency  of  an  electric  heater  is  100  per  cent,  since  all 


ELECTRICAL    HEATING  281 

the  current  that  is  passed  into  the  heater  is  dissipated  in 
the  form  of  heat  and  no  other  losses  are  experienced.  This 
is  not  true  of  steam  systems  where  the  water  of  condensa- 
tion is  thrown  away  at  fairly  high  temperatures.  Where 
electricity  or  steam  is  generated  and  distributed  all  in  the 
same  building,  there  is  no  line  loss  to  be  accounted  for, 
since  all  of  this  heat  goes  to  heating  the  building  and  counts 
as  additional  radiation. 

Equations  105  and  106  show  the  theoretical  relation 
existing  between  electrical  heating  and  hot  water  and  steam 
heating  compared  at  the  power  plant.  The  following  dis- 
cussion is  based,  therefore,  upon  the  assumption  that  1 
kilo-watt  hour,  in  an  electric  radiator,  will  give  off  the  same 
amount  of  heat  as  20.1  and  13.4  square  feet  of  hot  water  and 
steam  radiation  respectively.  With  coal  having  13000  B.  t.  u. 
per  pound  and  a  furnace  efficiency  of  60  per  cent.,  it  will 
require  3412  +  7800  =  .44  pound  of  coal  per  hour.  If  coal 
costs  $2.00  per  ton  of  2000  pounds,  there,  will  be  an  actual 
fuel  expense  of  .044  cent.  On  the  other  hand,  assuming  the 
combined  mechanical  efficiency  of  an  engine  or  turbo-gener- 
ator set  to  be  90  per  cent,  the  heat  from  the  steam  that  Is 
turned  into  electrical  energy  per  hour  is  1000  -4-  .90  =  1111 
watts,  'for  each  kilo-watt  delivered.  Now  if  this  unit  has 
15  per  cent,  thermal  efficiency,  we  have  the  initial  heat  in 
the  steam  equivalent  to  1111  -f-  .15  =  7400  watt  hours.  From 
this  obtain  7400  X  3.412  =  25249  B.  t.  u.  per  hour;  or,  25249 
-f-  7800  =  3.2  pounds  of  coal  per  hour.  This,  at  the  same 
rate  as  shown  above,  would  be  worth  .32  cent.  Comparing, 
the  electrical  generation  actually  costs  7.2  times  as  much  as 
the  other.  This  comparison  has  dealt  with  the  fuel  costs  at 
the  plant  and  has  not  taken  into  account  the  depreciation, 
labor  costs,  etc.,  the  object  being  to  show  relative  efficien- 
cies only. 

Another  way  of  looking  at  this  subject  is  as  follows. 
A  fairly  large  turbo-generator  set  (say  500  K.  W.)  will 
deliver  1  kilo-watt  hour  to  the  switchboard  on  20  pounds 
of  steam.  With  10  per  cent,  additional  steam  for  auxiliary 
units,  this  amounts  to  22  pounds  of  steam  per  kilo-watt  hour 
at  the  switchboard.  One  pound  of  steam  generated  in  a 
plant  of  this  kind  with  the  above  efficiencies  and  value  of 
coal,  also  with  a  steam  pressure  of  150  pounds  and  a  good 
feed  water  heater,  will  give  to  each  pound  of  steam  approxi- 
mately 1000  B.  t.  u.  This  makes  22000  B.  t.  u.  or  2.8  pounds 


282  HEATING  AND   VENTILATION 

of  coal  required  to  each  kilo-watt  output.     This  is  about  10 
per  cent,  less  than  the  above  figures. 

The  ratio  of  7  to  1,  as  shown  in  the  above  efficiencies, 
does  not  seem  to  hold  good  in  the  selling  price  to  the  con- 
sumer. In  round  numbers,  district  steam  and  hot  water 
heating  systems  supply  25000  B.  t.  u.  to  the  consumer  for 
one  cent.  The  cost  for  electrical  energy  to  the  consumer  is 
between  6  and  7  cents  per  kilo-watt.  This  gives  3412  -f-  6.5 
=  '525  B.  t.  u.  for  one  cent.  Comparing  with  the  above,  gives 
a  ratio  of  48  to  1. 

185.  The  Probable  Future  of  Electrical  Heating: — Be- 
cause of  the  low  efficiency  of  electrical  heating  as  compared 
to  other  methods  of  heating,  it  is  very  probable  that  it  will 
not  replace  the  other  methods  except  in  so  far  as  the  con- 
veniences of  the  user  is  the  principal  thing  sought  for,  and 
the  expense  of  operating  a  minor  consideration.  In  some 
forms  of  domestic  service,  however,  electrical  heating  is 
sure  to  find  considerable  usefulness.  The  temperatures  of 
low  pressure  steam  and  hot  water,  together  with  the  incon- 
venience of  use,  are  such  as  to  eliminate  them  from  many 
of  the  household  economies.  They  will  probably  continue 
to  be  used  for  house  heating,  water  heating  and  laundry 
work.  For  occupations  that  require  temperatures  above  250 
degrees,  such  as  broiling,  frying,  ironing,  etc.,  the  electrical 
supply  will  be  in  demand. 

Heating  by  electricity  on  a  large  scale  is  being  planned 
in  Stavanger,  Norway.  25000  horse-power  can  be  developed 
by  water  power.  This  will  be  turned  into  electrical  energy 
and  sold  at  $7.00  per  horse-power  year. 


REFERENCES. 
References  on   Electrical  Heating. 

TECHNICAL  PERIODICALS. 

The  Heating  and  Ventilating  Magazine.  Electrical  Heating 
and  Steam  Heating,  Feb.  1907,  p.  28.  Electric  Heating, 
W.  S.  Hadaway,  Jr.,  Nov.  1908,  p.  28;  Dec.  1908,  p.  26.  The 
Electrical  World,  Vol.  52,  pages  450,  903,  1112  and  1358,  and 
Vol.  53,  pages  5,  274  and  921.  The  Metal  Worker.  Electrical 
Heating  at  Biltmore,  N.  C.,  March  7,  1908,  p.  37.  Electric 
Heating  with  Fan  Blast  in  Paris,  Aug.  29,  1908,  p.  55.  Cool- 
ing and  Electric  Heating  on  Ship  Board,  Sept.  15,  1906;  Sept. 
22,  1906;  Oct.  6,  1906;  Nov.  21,  1908.  Unit  Cost  Limit  of  Elec- 
tric Heating,  Dec.  26,  1908,  p.  43.  Cost  of  Electric  and  Gas 
Cooking,  Aug.  29,  1909,  p.  50.  Electric  Heating  and  Steam 
Train  in  France,  Nov.  27,  1909,  p.  37.  Railway  Age  Gazette.  New 
Electric  Boiler,  June  20,  1910,  p.  1680.  Cassier's  Magazine. 
Electric  Heaters,  H.  M.  Phillips,  Dec.  1909. 


CHAPTER  XVI. 


REFRIGERATION. 


DESCRIPTION  OF  SYSTEMS  AND  APPARATUS. 

18G.  General  Divisions  of  the  Subject: — The  rapidly  in- 
creasing demand  for  the  cold  storage  of  food  products,  the 
production  of  artificial  ice  and  the  cooling  of  buildings  have 
developed  for  the  heating  engineer  a  broad  and  inviting 
field,  namely,  refrigeration.  A  municipal  electric  or  pump- 
ing station  with  a  district  heating  plant  to  utilize  the  ex- 
haust steam  in  winter  and  a  refrigeration  plant  to  utilize 
the  same  in  summer  furnishes  a  unique  opportunity  for 
economic  engineering.  One  application  of  the  above  princi- 
ple where  a  10-ton  ice  plant  of  the  absorption  type  was  so 
operated  in  a  town  of  3500  population  and  earned  a  dividend 
of  13  per  cent,  on  the  investment,  is  proof,  if  any  is  needed, 
that  the  field  is  an  intensely  practical  one. 

As  in  heating  systems  there  must  be  sources  of  heat, 
circulating  mediums,  distributing  systems  and  delivering 
systems  whereby  the  carriers  give  up  their  heat  at  the 
proper  places  in  the  circuits,  so  in  -refrigerating  systems 
there  must  be  sources  of  minus  heat  or  of  heat  abstraction, 
circulating  mediums,  distributing  systems  and  receiving  sys- 
tems whereby  the  carriers  take  up  heat  at  the  proper  places 
in  the  circuits  from  articles  or  rooms  that  are  being  cooled. 
The  carriers  (circulating  mediums),  and  the  receiving  and 
transmitting  of  the  heat  to  and  from  them  present  no  special 
difficulties  or  great  diversity  of  practice,  but  in  the  methods 
of  producing  and  maintaining  the  sources  of  minus  heat 
there  are  considerable  differences  and  numerous  methods. 

187.  Refrigerating  Systems  may  be  divided  into  two 
groups,  those  producing  cold  by  more  or  less  chemical  action 
between  ingredients  upon  mixing,  called  chemical  systems,  and 
those  producing  cold  by  the  evaporation  of  a  liquified  gas 
or  the  expansion  of  a  compressed  gas,  called  mechanical  sys- 
tems. Chemical  systems  are  used  only  occasionally  in  com- 
mercial work,  but  are  frequently  found  in  small  sized  plants 
for  domestic  purposes.  Low  first  cost  and  convenience  of 
handling  are  the  principal  advantages.  This  division  in- 
cludes the  .simple  melting  of  ice  and  the  mixing  of  ice  and 


284 


HEATING  AND    VENTILATION 


salt  for  temperatures  as  low  as  0  to  — 5  degrees.  The  latter 
is  much  used  in  domestic  processes  for  the  production  of 
table  ices,  etc.  Other  ingredients  used  in  the  mixtures  with 
the  corresponding  temperature  drops  which  may  be  ex- 
pected are  given  in  Table  53,  Appendix.  The  chemical 
method  of  producing  cold  is  occasionally  used  to  maintain 
low  temperatures  in  storage  rooms  while  repairs  are  being 
made  upon  the  regular  machinery.  The  chemical  methods 
of  cooling  are  so  simple  in  principle  that  they  will  not  be 
discussed  further  in  this  work.  Mechanical  systems  include 
all  the  practical  methods  of  commercial  refrigeration.  These 
are,  the  vacuum  system,  the  cold  air  system,  the  compression  system 
and  the  absorption  system, 

188.  Vacuum    System: — This    ^system    was    formerly    of 
some  importance  but  of  late  years  has  given  place  to  other 
and  more  efficient  methods.     Fig.   129   shows   a  vacuum  sys- 
tem in  diagram.     If  a  spray  of  water 
or  brine   is  injected  into  a  chamber 
that  contains  pans  of  sulphuric  acid 
and  is  kept  at  a  partial   vacuum  of 
one  or  two  ounces,  the  acid  absorbs 
the  water  vapor  from  the  spray,  thus 
assisting  in  maintaining  the  vacuum 
and  lowering  the  temperature  of  the 
remainder  of  the  spray.     The  vapor- 
ization of  the  part  that  is  absorbed 
by    the     acid     requires     heat.       This 
heat  is  taken  from  the  liquid  of  the 
spray    that    is    not   absorbed,    conse- 
quently  the   temperature   of   the   re- 
maining   liquid    is    lowered.       In    a 
system    of   this    kind   a   temperature 
of    32    degrees    may    easily    be    ob- 
tained.     The    water    or    brine    after 
cooling    is    then    circulated    through 
the   coils    of   the   cold   storage    room 

where  it  takes  up  the  heat  of  the  rooms  and  contents  and 
returns  to  the  vacuum  chamber  to  be  again  partially  evapo- 
rated and  cooled. 

189.  Cold  Air  System: — The  cold  air  system  is  used  prin- 
cipally on  ship  board.   Fig.   130  shows  diagrammiatically  the 
parts  and  the  operation  of  the  system.     The  cycle  has  four 


REFRIGERATION 


285 


Fig.   130. 


parts,  compression  in  one  of  the  cylinders  of  the  compressor, 
cooling  in  the  air  cooler  by  giving  off  heat  to  the  cold  water 
thus  removing  the  heat  of  compression,  expansion  in  the  sec- 
ond cylinder  of  the  compressor  thus  cooling  the  air,  and 
refrigeration  in  the  cold  storage  room  where  the  heat  lost  dur- 
ing expansion  is  regained  from  the  articles  in  cold-storage. 
Cold  air  machines  work  at  low  efficiencies  because  of  the 
1  necessarily  large  cylinders  and  their  attendant  losses  due 
to  clearance,  heating  of  the  compression  cylinder,  snow  in 
the  expansion  cylinder  and  friction.  The  system  has  much 
to  recommend  it,  however,  since  it  is  extremely  simple,  occu- 
pies a  very  small  space  compared  with  other  systems  and 
uses  no  costly  gases,  chemicals  or  supplies. 

190.  The  Compression  and  the  Absorption  Systems  have 
in  common  this  fact — both  use  a  refrigerant,  i.  e.,  a  liquid  hav- 
ing a  comparatively  low  boiling  point.  Perhaps  the  most 
common  refrigerant  is  anhydrous  ammonia,  which  boils,  at 
atmospheric  pressure,  'at  28.5  degrees  below  zero  and  in 
doing  so  absorbs  as  latent  heat  573  B.  t.  u.  Table  54,  Ap- 
pendix, gives  further  properties.  Other  refrigerants  used 
•to  a  lesser  extent  are  sulphur  dioxide,  SO2,  which  boils  at 
-f-14  degrees  under  atmospheric  pressure  with  a  latent  heat 


286  HEATING  AND   VENTILATION 

of  162  B.  t.  u.  and  carbon  dioxide,  CO2,  which  boils  at  — 3C 
degrees  under  a  pressure  of  182  pounds  per  square  inch 
absolute  with  a  latent  heat  of  140  B.  t.  u.  A  comparison  of 
the  temperatures  and  pressures  of  four  common  refriger- 
ants is  given  in  Table  59,  Appendix.  Pictet's  fluid  is  a  mix- 
ture of  97  per  cent,  sulphur  dioxide  and  3  per  cent,  carbon 
dioxide. 

A  choice  of  a  universal  refrigerant  can  scarcely  be  made 
because  of  the  varying  conditions  of  individual  plants.  The 
principal  difficulty  with  the  use  of  sulphur  dioxide  is  the 
fact  that  any  water  uniting  with  it  by  leakage  immediately 
produces  sulphurous  acid  with  its  corroding  action  upon  all 
the  iron  surfaces  of  the  system.  This  same  objection  holds 
also  for  Pictet's  fluid.  The  objections  to  the  use  of  carbon 
dioxide  are,  first,  its  comparatively  low  latent  heat,  and 
second,  the  high  pressure  to  which  all  parts  of  the  apparatus 
and  piping  are  subjected.  Pressures  of  from  300  to  900 
pounds  per  square  inch  are  very  common.  Perhaps  the  worst 
charge  that  can  be  made  against  ammonia  as  a  refrigerant 
is  that  it  is  highly  poisonous  and  corrodes  metals,  particu- 
larly copper  and  copper  alloys.  However,  the  high  latent 
heat  of  ammonia,  together  with  the  fact  that  its  pressure 
range  is  neither  so  high  as  with  carbon  dioxide,  nor  so  low 
as  with  sulphur  dioxide,  are  perhaps  the  chief  reasons  for 
the  very  general  preference  for  ammonia  as  the  commercial 
refrigerant  in  compression  systems;  while  its  great  affinity 
for  and  solubility  in  water,  are  what  make  the  absorption 
system  a  possibility. 

191.  Compression  System: — Compression  machines  may 
work  well  with  the  use  of  any  one  of  the  four  refrigerants  of 
Table  59,  df  the  proper  pressures  and  temperatures  are  ob- 
served and  maintained.  The  common  refrigerant  for  this 
type  is,  however,  anhydrous  ammonia,  for  reasons  given 
above.  Fig.  131  shows  a  diagrammatic  sketch  of  the  com- 
pression system.  To  follow  the  closed  cycle  of  the  ammonia, 
start  with  a  charge  being  compressed  in  the  cylinder  of  the 
compressor.  From  this  it  is  conveyed  by  pipe  to  the  con- 
denser which,  being  cooled  by  water,  abstracts  the  latent 
heat  of  the  refrigerant  and  condenses  it  to  a  liquid.  From 
the  condenser  the  liquid  refrigerant  is  conveyed  to  the  ex- 
pansion valve  through  which  it  expands  into  the  evaporator 
or  brine  cooler.-  In  changing  from  a  liquid  to  a  ga,s  in  the 
evaporator  it  absorbs  from  the  brine  an  amount  of  heat 


REFRIGERATION 


287 


REFRIGERATOR 
ROOM  AT  30 


COCLINC  WATER 


LIQUID  AMnONIA    £xf*NSION  VALVE    LIQUID  AMMONIA 

Fig.  131. 


equivalent  to  the  heat  of  vaporization  of  the  ammonia. 
Upon  leaving  the  evaporator  the  refrigerant  is  again  ready 
for  the  cylinder  of  the  compressor,  thus  completing  the 
cycle. 

If  the  refrigerant  is  ammonia,  the  compressor  is  com- 
monly of  the  vertical  type,  direct  connected  to  a  horizontal 
Corliss  engine  as  shown  in  Fig.  132.  This  type  of  com- 


TEN  TON  AMMONIA  COMPRESSOR 

Fig.   132. 


UNIVERSITY  OF  NEBRASKA 


pressor  combines  the  high  efficiency  of  the  Corliss  engine 
with  the  vertical  type  of  compressor  which  is  probably  the 
best  type  for  reliable  service  of  valves  and  pistons.  The 
vertical  compressor  is  usually  single  acting  with  water 
jacketed  cylinders.  Horizontal  compressors  are  usually 
double  acting,  as  shown  in  Fig.  133,  where  the  prime  mover 


288 


HEATING  AND   VENTILATION 


Fig.   133. 


is  a  direct  connected  electric  motor.  Poppet  valves  in  this 
type  are  placed  at  an  angle  of  30  degrees  to  45  degrees  with 
the  center  line  of  the  cylinder,  a  construction  made  neces- 
sary by  space  restrictions  on  the  cylinder  heads.  Compres- 
sors for  other  refrigerants  are  commonly  of  these  same 
types,  the  main  difference  being  that  compressors  for  carbon 
dioxide  systems  are  nearly  always  two-stage  to  produce 
high  compressions.  The  intermediate  cooler  pressures  range 
from  300  to  600  pounds  per  square  inch.  Horizontal  steam 


I        I    111  I        i|l   I1    |I.H" 

•LIM 


'   -7 


Fig.  134. 


REFRIGERATION 


289 


cylinders  in  tandem  with  the  compressor  cylinders  are  com- 
mon for  the  carbon  dioxide  systems  and  the  compressor  cyl- 
inders are  usually  single  acting. 

192.  Condensers  for  Compression  Systems  are  classi- 
fied under  four  heads,  atmospheric  condensers,  'Concentric 
tube  condensers,  enclosed  condensers  and  submerged  conden- 
sers. An  elevation  of  an  atmospheric  condenser  is  shown  in 
Fig.  134.  As  illustrated  it  consists  of  vertical  rows  of  pipes 
so  connected  by  return  bends  as  to  make  the  hot  refrigerant 
pass  through  each  pipe  beginning  at  the  top,  while  the  cold 
water  main  at  the  top  of  the  row  furnishes  a  spray  of  water 
which  trickles  over  the  outside  of  the  pipes.  The  gas  on 
the  inside  of  the  pipes  is  thus  cooled  by  the  extraction  of 
the  quantity  of  heat  that  is  used  in  raising  the  temperature 
of  the  water  and  evaporating  a  part  of  it.  The  complete  con- 
denser may  consist  of  any  required  number  of  these  vertical 
rows,  placed  side  by  side,  each  row  properly  connected  to 
the  hot  gas  header  and  to  the  liquid  header. 

An  elevation  of  one  section  of  a  concentric  tube  condenser  is 
shown  in  Fig.  135.  The  arrows  show  the  paths  of  the  gas 
and  water.  As  in  the  atmospheric  type  the  gas  enters  at  the 
top  and  the  liquid  is  drawn  off  below.  In  its  descent  it 


290 


HEATING   AND   VENTILATION 


passes  through  the  annular  space  between  the  two  concen- 
tric pipes  and  is  cooled  by  the  atmosphere  on  the  outside  of 
the  larger  pipes  and  by  the  water  circulating  through  the 
inner  pipes.  This  condenser  has  the  advantage  over  the  sim- 
ple atmospheric  condenser  in  that  the  water  may  be  made  to 
have  an  upward  course  through  the  apparatus,  thus  bring- 
ing the  coldest  water  in  contact  with  the  pipes  carrying  the 
liquid  rather  than  with  the  pipes  carrying  the  hot  gas. 
Since  the  efficiency  of  the  plant  as  a  whole  is  very  largely 
dependent  upon  the  temperature  of  the  liquid  at  the  expan- 
sion valve  this  matter  of  the  "counter  flow"  of  the  cooling 
water  is  an  important  one.  Fo<r  the  medium  sized  and  large 
compression  systems  this  form  of  condenser  is  used  almost 
without  exception. 

The  enclosed  condenser,  Fig.  136,  is  very  similar  to  the  sur- 
face coil  condenser  in  steam  engine 
plants.  It  'consists  of  a  cylindrical 
chamber  with  a  number  of  concen- 
tric pipe  spirals  connecting  a  hot 
water  header  at  the  top  with  a  cold 
water  header  at  the  bottom  of  the 
cylinder.  The  pipes  of  the  spirals 
are  provided  with  stuffing  boxes 
where  they  pierce  the  upper  and 
lower  heads  of  the  cylinder.  With 
this  condenser  a  counter  flow  of 
the  water  is  used,  the  cold  water  en- 
tering the  bottom  of  the  coils  and 
flowing  upward,  so  that  the  liquid  re- 
frigerant at  the  bottom  of  the  cylin- 
der is  very  near  the  temperature  of 
the  incoming  water. 

A  submerged  condenser,  as  the  name 
implies,  contemplates  a  rather  large 
body  of  water  below  the  surface  of 
which  there  is  submerged  a  coil  for 
circulating  the  hot  refrigerant.  Fig. 
137  shows  a  section  of  such  a  con- 
denser.  The  hot  gas  enters  at  the 
top  fitting  of  the  coil  and  leaves  at 

lower  fitting.  Cold  water  is  constantly  flowing  in  at  the  bot- 
tom of  the  tank  and  leaving  by /the  overflow  at  the  top,  being 
heated  as  it  rises.  The  form  of  the  coil  is  usually  spiral, 


REFRIGERATION 


291 


although  this  condenser  may  be  built  with  coils  of  the  re- 
turn bend  type  when  larger  surface  is  required.  Only  the 
smaller  compression  plants  use  the  enclosed  or  the  sub- 
merged type  of  condenser. 


Fig.  137. 

In  general,  condensers  may  be  considered  vital  factors 
in  the  economy  of  compression  plants.  They  must  be  reliable 
in  service  and  economical  in  operation,  and  must  be  so  de- 
signed and  proportioned  that  they  will  deliver  liquid  re- 
frigerant within  five  degrees  of  the  temperature  of  the  in- 
coming cooling  water.  A  condenser  should  present  all 
joints,  particularly  those  holding  the  refrigerant,  to  plain 
view  for  easy  inspection  and  repair.  Since  it  is  the  func- 
tion of  the  condenser  to  dissipate  the  heat  of  the  refrigerant 
gas,  it  is  not  uncommon  to  install  it  upon  the  roof  or  out- 
side the  building  in  some  cool  place.  This  is  especially  true 
where  the  atmospheric  or  the  concentric  tube  types  are 
used.  In  such  positions  the  heat  radiated  by  the  condenser 
is  not  given  back  to  the  rooms  and  piping  systems.  In  addi- 
tion, the  cooling  action  of  the  atmosphere  'assists  in  making 
the  system  more  efficient. 


292  HEATING  AND  VENTILATION 

193.  Evaporators  for  compression  systems  may  be  con- 
sidered as  condensers,  reversed  in  action  but  very  similar 
in  form.  If  the  refrigerating  effect  is  accomplished  by  the 
brine  cooling  system  an  evaporator  of  some  type  will  be 
necessary,  but  if  the  refrigeration  is  accomplished  by  circu- 
lating the  expanding  refrigerant  itself,  no  evaporator  is  re- 
quired. Evaporators,  or  brine  coolers,  may  be  classified 
according  to  the  method  of  construction,  as  shell  coolers  and 
concentric  tube  coolers. 

The  shell  cooler  takes  various  forms.  One  is  shown  by 
Fig.  136,  being  in  effect  an  enclosed  condenser  with  brine 
instead  'Of  cold  water  circulating  in  the  coils.  The  heat  of 
the  brine  is  transferred  to  the  cool  liquid  refrigerant,  caus- 
ing the  refrigerant  to  evaporate  and  take  from  the  brine 
an  amount  of  heat  equal  to  the  latent  heat  of  the  refriger- 
ant. The  proper  height  to  which  the  liquid  refrigerant 
should  be  allowed  to  rise  in  the  evaporator  is  a  very  much 
disputed  point,  some  -old  and  experienced  operators  claim- 
ing greatest  efficiency  when  about  one-third  of  the  cooling 
surface  is  covered  with  liquid  refrigerant  leaving  two- 
thirds  to  be  covered  with  gaseous  refrigerant.  Others  claim, 
that  the  entire  surface  should  be  covered  or  "flooded"  with 
liquid  refrigerant.  These  points  of  view  give  rise  to 
the  two  terms  dry  systems  and  flooded  systems.  Of  late  years 
the  flooded  systems  are  gaining  somewhat  in  favor,  a  sepa- 
rator being  installed  between  the  evaporator  and  the  com- 
pressor to  prevent  any  liquid  being  drawn  into  the  com- 
pressor cylinder.  This  'Separator  drains  any  liquid  which 


Fig.  138. 


REFRIGERATION  292 

may  collect  therein,  back  into  the  evaporator.  In  the  flooded 
system  the  brine  cooler  more  commonly  takes  the  form 
shown  in  Fig.  138,  where  at  the  end  A  D  of  the  brine  tank 
AliCD  is  shown  the  flooded  cooler  E.  This  cooler  consists 
of  a  boiler  shell  filled  with  tubes,  the  brine  circulating 
through  the  inside  of  the  tubes  while  the  interior  of  the 
large  shell  is  nearly  or  quite  filled  with  liquid  refrigerant. 

Concentric  tube  brine  coolers  are  made  of  piping  very  similar 
in  principle  to  that  shown  in  Fig.  135,  with  the  exception 
that  instead  of  two  concentric  pipes,  three  are  more  com- 
monly employed.  The  brine  circulates  through  the  inner- 
most of  the  three  and  through  the  outermost,  while  the 
annular  space  between  the  smallest  pipe  and  the  middle 
pipe  is  traversed  by  the  liquid  refrigerant.  In  this  way 
the  annular  space  filled  with  refrigerant  has  brine  on  both 
sides  and  the  cooling  of  the  brine  is  very  rapid.  The  numer- 
ous joints  in  this  cooler  present  a  constant  source  of  trouble. 
Salt  brine  will  usually  freeze  in  the  inner  pipe,  so  that  cal- 
cium chloride  brine  must  be  used. 

A  choice  of  evaporators  or  coolers  depends  mainly  upon 
whether  the  plant  is  to  run  continuously  or  intermittently. 
When  run  continuously  only  a  small  amount  of  brine  is 
required  and  this,  when  cooled  quickly  and  circulated 
quickly,  would  call  for  a  concentric  tube  cooler.  When  run 
intermittently  a  much  larger  body  of  brine  is  desirable  so 
as  to  remain  cool  longer  during  the  night  hours  when  the 
plant  is  not  operating.  For  this  condition  a  shell  type 
cooler  would  probably  be  preferred. 

In  addition  to  the  condensers  and  evaporators  that  were 
described  in  detail,  there  are  to  be  found  on  the  well  equip- 
ped compression  system  the  following  pieces  of  apparatus 
which  will  be  mentioned  and  described  only  briefly.  An  oil 
separator  is  commonly  found  in  the  line  connecting  the  con- 
denser with  the  compressor.  This  is  simply  a  large  cast 
iron  cylinder  with  baffle  plates  to  separate  the  oil  from  the 
ammonia.  Since  the  oil  is  heavier  than  the  ammonia  it  set- 
tles to  the  bottom  and  may  be  drawn  off.  An  ammonia  scale 
strainer  is  often  found  just  before  the  compressor  intake. 
Small  purge  valves  are  located  at  all  high  points  in  the 
system  for  the  purpose  of  exhausting  the  foul  gases  or  the 
air  which  may  collect  in  the  system.  Such  >a  purge  con- 
nection is  shown  on  the  right  end  of  the  upper  coil  in 
Fig.  134. 


294 


HEATING  AND   VENTILATION 


104.  Pipes,  Valves  and  Fittings  for  compressor  refriger- 
ant piping  are  considerably  different  from  the  standard  types, 
If  the  refrigerant  is  ammonia,  no  brass  enters  into  the  de- 
sign of  any  part  of  the  piping  or  auxiliaries  traversed  by  the 
ammonia.  The  operating  principles  of  all  valves  are  the 
same  as  standard  ones  but  they  are  made  heavier  and  en- 
tirely of  iron,  or  iron  and  aluminum.  The  common  threaded 
joint  used  on  all  .standard  fittings  is  replaced  in  ammonia 
systems  by  the  bolted  and  packed  joint.  It  is  not  within  the 
scope  of  this  work  to  go  into  these  details  further  than  to 


Fig.   139.  Fig.   140. 

give  a  section  of  an  ammonia  expansion  valve,  Fig.  139,  and 
a  section  of  a  typical  ammonia  joint,  Fig.  140. 

195.  Absorption  System: — As  stated  in  Art.  190,  the 
great  affinity  of  ammonia  gas  for  water  and  its  solubility 
therein,  are  what  make  the  absorption  system  a  possibility 
and  give  it  the  name  as  well.  At  atmospheric  pressure  and 
50  degrees  temperature  one  volume  of  water  will  absorb 
about  900  volumes  of  ammonia  gas.  At  atmospheric  pres- 
sure and  100  degrees  temperature  one  volume  of  water 
will  absorb  only  about  one-half  as  much  gas,  or  450  vol- 
umes. If  then,  one  volume  of  water  is  saturated  at  50  de- 
grees with  ammonia  gas  and  heated  to  100  degrees  there 
Will  be  liberated  about  450  volumes  of  ammonia  gas.  Hence 
it  is  evident  that  a  stream  of  water  may  be  used  as  a  con* 
veyor  of  ammonia  gas  from  one  place  or  condition  to  an- 
other, say  from  a  condition  of  low  temperature  and  pres- 
sure where  the  absorbing  stream  of  water  would  be  cool,  to 


REFRIGERATION 


295 


a  condition  of  high  temperature  and  pressure,  where  the 
gas  would  be  liberated  by  simply  heating  the  water.  It  will 
be  noticed  that  the  gas  has  been  transferred  as  a  liquid 
without  a  compressor  or  any  compressive  action,  by  pump- 
ing a  stream  of  water  of  approximately  one-four  hundred 
and  fiftieth  of  the  volume  of  the  gas  transferred.  This,  in 
the  abstract,  is  the  method  employed  in  the  absorption 
system  to  convey  the  ammonia  gas  from  the  relatively  low 
temperature  and  pressure  of  the  evaporator  to  the  high 
temperature  and  pressure  at  the  entrance  of  the  condenser. 
The  absorption  system,  when  closely  compared  in  prin- 
ciples of  operation  to  the  compression  system,  differs  only 
in  one  respect,  namely,  the  absorption  system  replaces  the 
gas  compressor  by  the  strong  and  weak  liquor  cycle.  As 

shown  in  Fig.  141,  both  sys- 
tems   have   arrangements    of 
condenser,     expansion    valve 
and  evaporator  that  are  iden- 
tical,   hence   the   part   of   the 
cycle  through  these  need  not 
be  considered.     The  problem 
of  completing  the  cycle  from 
evaporator      t  o      condenser, 
however,  is  solved  quite  dif- 
ferently in  the  two  systems. 
In    the    compression    system 
(upper  diagram)    the   evapo- 
rator  delivers   the    expanded 
gas  to  the  compres- 
sor,     from      which, 
under     high      pres- 
sure   and    tempera- 
ture, it  is  delivered 
to      the      condenser 
and     the     cycle     is 
completed.      In    the 
absorption       system 
(lower     diagram) 
the    evaporator    de- 
livers the  expanded 
gas  to  an  absorber, 
in     which     the     gas 
comes      in      contact 
with  a  spray  of  so- 
called     weak     liquor, 


296  HEATING  AND  VENTILATION 

consisting  of  water  containing  about  15  to  20  per 
cent,  of  anhydrous  ammonia.  The  weak  liquor  absorbs 
the  ammonia  gas  through  which  the  liquor  is  sprayed  and  col- 
lects in  the  upper  part  of  the  absorber  as  strong  liquor,  contain- 
ing about  twice  as  much  anhydrous  ammonia  as  the  weak 
liquor,  or  30  to  35  per  cent.  From  here  it  is  pumped  through  the 
exchanger  (which  will  be  ignored  for  the  present)  into  the 
generator  at  a  pressure  of  about  170  pounds  per  square  inch 
gage.  In  the  generator  heat  is  supplied  by  steam  coils  im- 
mersed in  the  strong  liquor.  As  this  liquor  is  heated  it 
gives  up  about  half  of  the  contained  ammonia  gas  which 
rises  and  passes  from  the  generator  to  the  condenser,  thus 
completing  the  ammonia  or  primary  cycle,  while  the  weak 
liquor  flows  from  the  bottom  of  the  generator  through  the 
exchanger  and  pressure  reducing  valve  back  to  the  ab- 
sorber, thus  completing  the  secondary  or  liquor  cycle. 

In  general  then,  the  absorption  system  uses  two  cycles, 
that  of  the  ammonia  and  that  of  the  liquor,  the  paths  of  the 
two  cycles  being  coincident  from  the  absorber  to  the  gen- 
erator. The  liquor  pump  serves  to  keep  both  cycles  in  mo- 
tion. The  pump  creates  the  pressure  for  both  cycles  and 
the  expansion  valve  and  the  reducing  valve  reduce  the 
pressure  respectively  for  the  ammonia  cycle  and  the  liquor 
cycle.  The  exchanger  does  not  mix  or  alter  the  condition  of 
the  two  streams  of  liquor  passing  through  it,  for  its  only 
function  is  to  bring  these  two  streams  close  enough  that 
the  heat  of  the  weak  liquor  from  the  generator  may  be  trans- 
ferred to  the  strong  liquor  going  to  the  generator.  Stated  in 
other  words,  the  exchanger  heats  the  strong  liquor  by  cool- 
ing the  weak  liquor,  thus  effecting  a  saving  of  heat  which 
would  otherwise  be  lost,  since  the  weak  liquor  must  be 
cooled  before  it  is  ready  to  properly  absorb  the  gas  in  the 
absorber. 

196.  An  Elevation  of  an  Absorption  System  with  the 
elements  piped  according  to  what  is  considered  best  prac- 
tice is  shown  in  Fig.  142.  Starting  at  the  expansion  valve, 
the  ammonia  (liquid,  gas  or  gas  in  solution)  passes  in  order 
through  these  pieces  of  apparatus:  the  evaporator,  the  ab- 
sorber, the  liquor  pump,  the  chamber  of  the  exchanger  or  the 
coil  of  the  rectifier,  the  generator,  the  chamber  of  the  recti- 
fier and  the  condenser  back  to  the  expansion  valve.  At  the 
same  time  the  liquor  used  to  absorb  the  gas  travels  in  order 
through  these  pieces:  the  absorber,  the  liquor  pump,  the 


REFRIGERATION 


±=>COLO  BRINE   TO  REFRCERWQR 
0°     0° 


"^=~     ~~CyJ     f 
.. PRESS  RE  DV  AL  VC 


Fig.  142. 

chamber  of  the  exchanger  or  the  coil  of  the  rectifier,  the 
generator,  the  pressure  reducing  valve  and  the  coil  of  the 
exchanger  back  to  the  absorber.  The  method  of  pipe  connec- 
tions shown  is  a  very  common  one  although  some  varia- 
tion may  be  found,  especially  in  the  continued  use  of  cool- 
ing water  in  consecutive  pieces  of  apparatus.  As  shown, 
the  cooling  water  is  first  used  in  the  condenser.  This  will 
be  found  so  in  all  plants.  From  the  condenser  the  cooling 
water  may  next  be  taken  to  the  absorber,  as  shown  in  the 
sketch,  or  it  may  be  used  in  the  rectifier  .coil  instead  of  the 
strong  liquor.  In  recent  years  the  practice  of  by-passing 
a  certain  amount  of  the  cool,  strong  liquor  from  the  pump 
through  the  rectifier  is  gaining  in  favor.  Fig.  142  shows 
a  plant  having  bent  coil  construction.  Plants  are  also  built 
having  straight  pipe  construction,  where  all  coil  surfaces 
shown  are  replaced  by  straight  pipes,  the  condenser  being 
usually  of  the  concentric  tube  atmospheric  type  and  the 
evaporator  being  also  of  the  concentric  tube  brine  cooler 
type,  as  mentioned  under  compression  systems.  Both  types 
of  absorption  plants  are  found  in  use. 


298 


HEATING   AND   VENTILATION 


197.      Generators   are   classified   as   horizontal   and   verti- 
cal.     Fig.    143   shows   a   horizontal   type   generator,   with   the 


Fig.  143. 

analyzer  and  exchanger,  and  Fig.  144  shows  the  vertical 
type,  also  with  the  analyzer.  The  horizontal  type  may  have 
one  or  more  horiontal  cylinders  equipped  with  steam  codls. 
The  analyzer,  which  may  be  considered  as  an  enlarged  dome 
of  the  generator,  is  used  to  condense  the  water  vapor  which 
rises  from  the  surface  of  the  -liquid  in  the  generator.  To 
do  this  the  analyzer  has  a  series  of  horizontal  baffle  plates 
through  which  the  incoming  cool,  strong  liquor  trickles 
downward  while  the  heated  mixture  of  ammonia  gas  and 
water  vapor  passes  upward  through  interstices.  In  this 
way  the  strong  liquor  gradually  cools  the  ascending  water 
vapor  and  condenses  much  of  it  on  the  surfaces  of  the 
baffle  plates. 

198.  Rectifiers  are  arrangements  of  cooling  surface 
designed  to  thoroughly  dry  the  gas  just  before  it  passes 
into  the  condenser.  This  is  accomplished  by  presenting 
to  the  hot  product  of  the  generator  just  enough  cooling  sur- 
face to  condense  'the  water  vapor  without  condensing  any  of 


REFRIGERATION 


299 


Fig-.    144. 


the  ammonia  gas.  Rectifiers  are 
very  similar  in  general  design  -to 
the  various  types  of  condensers, 
there  being  atmospheric,  concen- 
tric tube,  enclosed  and  submerged 
rectifiers  just  as  there  are  these 
same  type  of  condensers,  each  de- 
scribed under  the  head  of  con- 
densers for  compression  systems. 
Rectifiers  may  save  he<a<t  by  the 
arrangement  shown  in  Fig.  142, 
where  the  iheat  abstracted  from  the 
water  vapor  is  given  to  the  cool, 
strong  liquor  before  entering  the 
generator.  As  shown,  the  .strong 
liquor  may  be  divided,  part  pass- 
ing through  the  rectifier  and  part 
through  the  exchanger,  or  the 
strong  liquor  may  all  go  through 
the  exchanger  first  and  then 
through  the  rectifier.  Where 
strong  liquor  is  so  used,  the  recti- 
fier is  always  of  the  enclosed 
type.  Reotifiers  using  water  as 
the  cooling  medium  are  often 
called  dehydrators,  the  /term  -  rec- 
tifier being  more  properly  used 
when  the  cooling  medium  is  the 
strong  liquor. 

199.  Condensers  for  absorption 
systems  do  not  differ  in  design 
from  those  used  for  compression 
systems.  The  same  types  are  used, 
and  in  'the  same  manner,  the  sur- 
face being  somewhat  less  due  to 
the  precooling  effect  of  the  recti- 
fiers or  dehydrators.  As  a  gen- 
eral statement,  it  is  claimed  that 
from  20  to  25  per  cent  less  surface 
is  required  in  the  condenser  for  an 
absorption  machine  than  is  re- 
quired in  one  for  a  compression 
machine. 


300 


HEATING  AND   VENTILATION 


200.  Absorbers  may  be  classified  as  dry  absorbers,  wet 
absorbers,  atmospheric  absorbers,  concentric  tube  absorb- 
ers and  horizontal  and  vertical  tubular  absorbers.  In  the 
dry  absorber,  the  top  section  of  which  is  shown  in  Fig.  145, 

the  weak  liquor  enters  at  the 
middle  of  the  top  header  and 
is  sprayed  upon  a  spray  pan, 
from  which  it  drips  downward 
over  the  coils.  The  gas  enters 
as  shown,  part  being  delivered 
above  the  spray  plate,  so  as  to 
come  into  contact  with  the 
spray  and  the  larger  part  being 
taken  downward  through  the 
central  pipe  to  a  point  near  the 
bottom  of  the  absorber,  from 
Fig.  145.  which  point  it  flows  upward 

against  the  descending  weak  liquor  by  which  it  is  absorbed. 
As  the  gas  is  dissolved  by  the  weak  liquor  the  heat  of  ab- 
sorption is  given  off,  and  taken  up  by  the  cooling  water  in 
the  coils.  The  result  is  a  strong  liquor  which  collects  in 
the  abS'Orber  ready  to  be  delivered  to  the  pump. 

The  wet  absorber,  on  the  contrary,  has  practically  the 
whole  body  filled  with  weak  liquor  and  the  ammonia  gas 
enters  near  the  bottom,  bubbling  up  through  the  weak 
liquor  thus  saturating  it.  Various  baffle  plates  with  fine 
perforations  break  up  the  gas  into  small  bubbles  thus  aid- 
ing in  presenting  a  large  surface  of  gas  to  the  liquor 
which,  as  it  becomes  saturated  and  lighter,  rises  to  the  top 
of  the  body  of  the  absorber  and  is  ready  to  be  drawn  off  by 
the  pump.  Instead  of  spiral  cooling  coils,  this  type  is  often 
made  with  straight  cooling  tubes  inserted  between  two  tube 
sheets,  boiler  fashion.  This  straight  tube  construction  is 
much  simpler  and  cheaper,  and  much  more  easily  cleaned 
than  the  spiral  type.  It  is  favored  by  some  on  this  account, 
especially  where  the  cooling  water  has  a  tendency  to  form 
scale. 

Atmospheric  absorbers  resemble  atmospheric  condensers  of 
the  single  tube  type.  The  ammonia  gas  and  weak  liquor  en- 
ter the  bottom  through  a  fitting  commonly  called  a  mixer, 
and  the  two  flow  upward  through  the  inside  of  the  pipe 
while  the  cooling  water  is  in  contact  with  the  outside  thus 
taking  up  the  heat  of  absorption  generated  within  the  pipes. 


REFRIGERATION  301 

Concentric  tube  absorbers  are  very  similar  in  design  to  con- 
centric tube  condensers,  the  cooling  water  passing  through 
the  central  tube  and  the  weak  liquor  and  expanded  gas  en- 
tering at  the  bottom  of  the  annular  space  and  circulating  to 
the  top,  .absorption  taking  place  on  the  way.  Because  of  the 
small  capacity  of  the  last  two  mentioned  absorbers,  it  is 
necessary  to  use  with  them  an  aqua  ammonia  receiver  be- 
tween the  absorber  and  the  ammonia  pump,  to  act  as  a 
reservoir  for  storing  a  reserve  supply  of  the  strong  liquor. 

Horizontal  and  vertical  tubular  absorbers  are  those  in  which 
the  cooling  surface  is  composed  of  straight,  horizontal  or 
vertical  tubes  inserted  between  tube  sheets,  the  cooling 
water  flowing  inside  the  tubes  and  the  absorption  taking 
place  within  the  drum  or  body  of  the  absorber. 

201.  Exchangers   may   be   of   two   types,   the   shell    type 
or  the  concentric  tube  type.     The  shell  type,  as  the  name  im- 
plies,  is  composed   of  a  main  body   or   shell   through  which 
circulates   the    strong   liquor   to    be    heated   and    within    this 
shell  is  a  coil  or  other  arrangement  of  heating  pipes  through 
which   the  hot,   weak  liquor  flows.     Fig.   142   shows  the   ele- 
mentary   arrangement    of    such    an    exchanger.      Concentric 
tube  exchangers  are  used  on  large  plants.     They  are  similar 
in   every   way   to   the   concentric  tube   condensers   shown    in 
Fig.    135,    with   the   exception    that    larger   pipes   are    needed 
for  the  exchangers.     The  cold,  strong  liquor  is  usually  car- 
ried through  the  pipes  and  the  hot,  weak  liquor  through  the 
annular    space.      The   great   advantage    of    this    type    of    ex- 
changer  is    the    same    as   that   of    the    concentric   tube    con- 
denser, namely,  the  counter  flow  of  the  two  streams.     With 
this  arrangement  the   total  transfer  of  heat  is  a  maximum, 
for  which   reason   this  type   of  exchanger  is   generally   pre- 
ferred. 

202.  Coolers    for    the    weak    liquor    are    often    found    in 
plants.     This  piece  of  apparatus  is  not  indicated  in  Fig.   142. 
It  is  usually  installed  as  the  lower  three  coils  of  the  atmos- 
pheric   condenser,    and    hence    is    simply    a    .small    condenser 
used  to  further  cool  the  weak  liquor  just  before  its  entrance 
into  the  absorber.     With  a  counter  flow,  concentric  tube  ex- 
changer a  weak  liquor  cooler  is  seldom  found  necessary. 

203.  The  Pump  used  in  absorption  systems  to  raise  the 
pressure  of  the  strong  aqua  ammonia  may  be  steam  driven, 
electric  driven   or   belt  driven,   as   best   suits    the   particular 

plant  conditions.     The  power  required  by  this  piece  of  appa 


302  HEATING  AND   VENTILATION 

ratus  is  about  one  horse  power  per  20  to  25  tons  of  refriger- 
ation capacity. 

204.  Compression  Systems  and  Absorption  Systems  Com- 
pared:— A  comparison  drawn  between  the  compression  sys- 
tem   and    the    absorption    system    brings    out    the    following 
facts.     The  compression  system  depends  fundamentally  upon 
the  transferring  of  heat  energy  into  mechanical  energy  and 
vice  versa,  with  the  attendant  heavy  losses.     The  absorption 
system    merely    transfers    heat   from    one   liquid    to   another. 
This  is  a  process  which  is  attended  by  only  moderate  losses. 
The   compression    system   is   comparatively   simple,    its   pro- 
cesses  readily   understood  and  its  machinery  easily  kept   in 
good   running  order.     The  absorption  system  is  complicated 
with  a  greater  number  of  parts,  its  processes  are  often  not 
thoroughly  understood  by  those  in  charge  and  its  machinery 
is  likely  to  become  inefficient  because  heat  transferring  sur- 
faces are  allowed   to   become   dirty.     For  these  reasons   the 
attendance  necessary  upon  an  absorption  plant  must  be  of  a 
higher   order   than  that   necessary  for  a  compression  plant. 

205.  Circulating  Systems! — The  refrigerating  effect  pro- 
duced by  either  one  of  the  two  systems  may  be  delivered  to 
the  place  of  application  in  two  ways.     The  first  is  the  brine 
circulation   metJiod    wherein    a    brine    cooler    is    used    through 
which  the  brine  flows  causing  the  evaporation  of  the  liquid 
refrigerant  and  the  cooling  of  the  brine.     This  cold  brine  is 
then  circulated  through  pipes  to  the  place  where  refrigera- 
tion is  desired.     Fig.  138  shows  an  evaporator  placed  in  one 
end  of  a  large  brine  tank.     The  refrigerating  effect  is  car- 
ried to  the  cans  o'f  water  by  the  circulation  of  this  body  of 
brine  through  the  evaporator  and  out  past  the  cans,  the  cir- 
culation  through   the   channels   shown   being   maintained   by 
the  pump.     Brine,  commonly  used  for  such  work,  is  made  by 
dissolving  calcium  chloride  in  water.     A  20  per  cent,   solu- 
tion  is   generally   used.      Salt   brine   is   used   to   some   extent 
but  it  has  many  disadvantages  compared  with  calcium  brine. 
The  second  method  is  the  direct  circulation  method  wherein  the 
liquid   refrigerant  is  conveyed  to  the  place  to  be  cooled,   is 
passed    through    an    expansion    valve    and    then    circulated 
through  coils  in  the  space  to  be  refrigerated,  changing  into 
gaseous    form    as    fast    as    it    can    absorb    enough    heat.      If 
ammonia  is  the  refrigerant  the  direct  circulation  is  not  often 
favored  because  of  its   highly   penetrative   nature  and   odor, 
even  a  leak  so  small  as  to  escape  detection  being  sufficient 


REFRIGERATION  303 

to    fill   the   refrigerated    space    with    the    odor,    which   'many 
food  stuffs  will  absorb. 

206.  There  are  Three  Methods  Employed  for  Maintain- 
ing  L.OW  Temperatures  in  storage  and  other  rooms.  The 
first  is  by  direct  radiation  where  the  pipes  are  placed  within 
the  room  and  the  refrigerant  is  circulated  -through  them. 
This  is  the  oldest,  simplest  and  cheapest  system  to  install. 
In  this  the  proper  location  and  arrangement  of  the  pipes  are 
essential  to  the  most  efficient  operation.  -Since  the  tempera- 
ture to  be  maintained  in  a  storage  room  depends  upon  the 
products  to  be  kept  in  the  room,  it  may  be  necessary  to  have 
a  considerable  range  of  temperature.  It  is  desirable  to  have 
the  pipes  arranged  as  coils  in  two  or  three  sets,  each  being 
valved  so  that  the  amount  of  refrigerant  being  circulated 
may  be  increased  or  decreased  as  the  temperature  of  the 
stored  product  may  require. 

The  pipes  should  be  set  out  from  the  wall  several  inches 
to  give  free  air  circulation  and  keep  the  frost  that  collects 
on  them  from  coming  into  contact  with  the  wall.  The  coils 
should  be  so  placed  that  the  temperature  of  all  parts  of  the 
room  may  be  kept  as  nearly  uniform  as  possible.  Some 
products  keep  as  well  in  still  air  as  when  it  is  in  motion,  but 
others,  such  as  fruits,  eggs,  cheese,  etc.  are  better  pre- 
served when  the  air  is  circulated.  Circulation  may  be  ef- 
fected in  a  room  piped  for  direct  radiation  by  putting  aprons 
over  the  coils  as  shown  in  Fig.  146.  These  aprons  consist  of 

12  inch  boards  D  nailed  to 
studding  E  and  the  whole 
fastened  to  the  coils,  the 
studding  serving  to  keep  the 
boards  from  coming  into 
contact  with  the  pipe  coils. 
A  false  ceiling  F  is  placed  a 
few  inches  below  the  ceiling 
of  the  room  so  that  the 
warm  air  flows  towards  the 
pipes  and  over  them,  drop, 
ping  to  the  floor  and  passing 
out  under  the  lower  edge  of 
the  apron  into  the  room. 

Fig.   146.  Wherever  direct  radiation  is 

used     drip     pans     should     be 

placed   directly   underneath   the   coils  in  order   to  catch  and 
drain  off  the  water  when  the  coils  are  cut  out  and  the  frost 


304 


HEATING  AND   VENTILATION 


melts.     This  water  should  be  drained  into  a  receptacle  that 

can  be  easily  emptied  when  filled. 

The  second  method  of  room  cooling  is  by  indirect  radiation. 

Let  Fig.  147  represent  a  section  of  a  storage  building.  The 
essential  parts  of  the  cooling  system  are, 
a  bunker  room  AC,  in  the  top  part  of  the 
building,  containing  the  cooling  coils 
B,  a  series  of  ducts  on  either  side  of  the 
building,  so  arranged  that  the  air  after 
passing  over  the  cooling  coils,  drops 
downward.  These  ducts  are  provided 
with  dampers  for  admitting  as  much  of 
the  cold  air  to  the  rooms  as  is  desired. 
On  becoming  warmed  this  air  is  crowded 
out  on  the  opposite  side  of  the  room  into 
the  ducts  K  and  rises  to  the  bunker- 
room  where  it  is  again  cooled  by  passing 
over  the  coils.  By  the  use  of  the  damp- 

t  I  £  illi  *>r  ''"''•  ers  *ne  col<*  air  mav  be  cut  off  from  any 
t^  lilt  k  :  room  or  admitted  in  large  quantities 
__^  ^  thus  making  it  an  easy  matter  to  main-- 
tain the  temperature  at  any  point  de- 
sired. The  ducts  leading  the  air  from 
the  rooms  should  be  25  per  cent,  larger 
than  the  ones  leading  to  the  rooms  and 
the  latter  should  have  about  three  square 
inches  cross-section  per  square  foot  of 
floor  area  in  rooms  having  a  ten  foot 
ceiling. 

The  third  method  is  by  means  of  a 
plenum  system  of  air  circulation,  Fig.  148.  The  arrangements 
are  quite  similar  to  those  of  the  plenum  system  for  heating, 

except  that  the  heating  coils 
are  replaced  by  the  refrigerat- 
ing coils.  The  air  required  for 
ventilation  is  blown  over  the 
icoil  surface,  erected  in  a  coil 
or  bunker  room,  over  which, 
oftentimes,  cold  water  is 
sprayed.  This  not  only  washes 
the  air  but  tends  to  lower  its 
temperature.  If  ammonia  is 
used  as  a  refrigerant,  brine  is 
circulated  in  the  coils,  but  if 


Fig.  147. 


Fig.  148. 


REFRIGERATION  305 

carbon  dioxide  is  used  direct  expansion  is  employed,  thus 
dispensing  with  the  use  of  brine.  The  principal  advantage 
of  the  plenum  system  of  cooling  is  that  a  positive  circulation 
of  air  may  be  maintained  in  any  room  even  though  the 
bunker  room  be  placed  on  the  first  floor  or  in  the  basement 
of  the  building.  This  is  the  system  used  in  large  buildings 
that  are  cooled  during  the  summer  as  well  as  heated  dur- 
ing winter,  in  factories  where  changes  of  temperature  seri- 
ously affect  the  product,  as  in  chocolate  factories,  in  fur 
storage  rooms,  in  drying  the  air  before  it  is  blown  into  blast 
furnaces  and  in  the  solution  of  many  other  important  eco- 
nomic problems. 

207.  Influence  of  the  Dew  Point: — In  cooling  a  building 
by  means  of  a  plenum  refrigerating  system,  great  trouble 
is  experienced  with  the  formation  of  ice  on  the  coils.  For 
example,  suppose  such  a  cooling  system  on  a  hot  summer 
day  is  taking  in  air  at  90  degrees  temperature  and  85  per 
cent,  humidity.  If  this  air  is  cooled  only  ten  degrees  (see 
chart,  page  29),  it  will  have  reached  its  dew  point  and  as 
the  cooling  continues  will  deposit  frost  and  ice  on  the  coils 
from  the  liberated  modsture,  the  air  meantime  remaining  at 
the  saturation  point  and  being  so  delivered  to  the  rooms.  The 
undesirable  feature  of  delivering  saturated  air  to  the  rooms 
may  be  avoided  by  cooling  only  part,  say  half  of  the  air 
stream,  considerably  lower  than  the  final  temperature  de- 
sired, and  then  mixing  it  with  the  other  half,  which  is 
drier,  before  delivering  it  to  the  rooms.  The  troublesome 
coating  of  ice  and  frost  on  the  pipes  may  be  avoided  by 
combining  the  cooling  system  with  the  air  washing  system 
and  using  a  brine  spray  instead  of  water  for  washing  the 
air  during  cooling.  The  brine,  which  freezes  at  a  very  low 
temperature  compared  with  water,  plays  over  the  cooling 
coils,  and  cleans  both  coils  and  air.  The  brine  should  pref- 
erably be  a  chloride  brine.  A  modification  of  this  method  of 
avoiding  ice  and  frost  is  to  provide  pans  above  the  coils 
and  fill  them  with  lumps  of  calcium  chloride.  The  pans 
have  perforations  so  arranged  that  as  the  strong  chloride 
solution  forms  (due  to  the  deliquescence  of  the  salt)  it 
trickles  down  over  the  pipes  and  holds  the  freezing  point 
of  any  collecting  moisture  far  below  the  temperature  of  the 
coils.  A  sketch  of  this  arrangement  is  shown  in  Fig.  149, 
which  has  the  disadvantage  of  the  clumsy  handling  of  the 
calcium  chloride.  Plants  operating  only  during  the  day,  as  for 


306 


HEATING  AND  VENTILATION 


Fig.  149. 


instance,  auditoriums,  commerce  chambers,  etc.,  often  have 
no  equipment  for  preventing  the  accumulation  of  frost  and 
ice,  it  being  allowed  to  form  during  the  short  period  of  use 
and  to  melt  during  the  period  of  rest. 

208.  Pipe  L,ine  Refrigeration: — In  a  number  of  the 
larger  cities  refrigeration  is  furnished  to  such  places  as 
cold  storage  rooms,  restaurants,  hotels,  auditoriums,  etc., 
by  a  conduit  system  or  central  station  system.  The  length 
of  the  mains  in  the  various  cities  where  used,  ranges  from 
a  few  hundred  feet  to  twenty  miles  and  the  circulating 
medium  employed  is  either  liquid  ammonia  or  brine.  In  the 
ammonia  system  two  pipes  are  used,  one  carrying  the  liquid 
ammonia  to  the  place  desired  and  the  other  returning  it 
after  expansion  to  the  central  station.  When  brine  is  used 
it  is  good  practice  to  circulate  it  at  from  12  to  15  degrees  F. 
Occasionally  the  conduits  carry  three  parallel  pipes,  two  of 
which  are  for  circulating  the  brine  and  the  third  is  for 
emergency  cases.  The  line  should  be  divided  into  sections, 
with  valves  and  by-passes  so  arranged  that  a  defective  sec- 
tion could  be  repaired  without  interfering  with  the  other 
parts.  All  valves  should  be  readily  accessible  and  all  high 
points  in  the  system  should  be  equipped  with  purge  valves. 


REFRIGERATION 


307 


The    service    pipes    should    be    two    inches    in    diameter    and 
well  insulated. 

Either  the  ammonia  absorption  or  compression  system 
may  be  used  for  cooling  the  brine  but  according  to  Mr.  Jos. 
H.  Hart,  the  latter,  making  use  of  direct  expansion,  is  the 
most  efficient  and  the  one  most  commonly  installed.  The 
loss  by  radiation  to  the  pipes  in  the  conduits  is  not  great  but 
numerous  mechanical  difficulties  are  yet  to  be  overcome.  It 
would  seem  desirable  to  make  the  pipe-line  system  of  cool- 
ing general  for  residence  use  but  as  yet  it  has  not  been 

found  economical  to  cool  build- 
ings using  less  than  the 
equivalent  of  500  pounds  of  re- 
frigeration in  24  hours.  Al- 
though not  an  efficient  method, 
it  seems  probable  that  cold  air 
refrigeration  by  using  balanced 
expansion  may  supersede  the 
other  systems. 

209.  As  a  Final  Application 
of  refrigeration  we  may  men- 
tion  the  cooling  of  the  drinking 
water  supply  in  large  office 
buildings,  hotels,  etc.  Usually 
this  is  simply  a  small  part  of 
the  work  of  a  large  refrigerat- 
ing plant.  Fig.  150  gives  a  dia- 
grammatic elevation  of  such  an 
arrangement. 
Fig.  150. 


CHAPTER  XVII. 


REFRIGERATION   CALCULATIONS. 


210.  Unit     Measurement     of     Refrigeration: — Since     the 

first  efforts  toward  refrigeration  employed  the  simple  pro- 
cess of  melting  ice  by  the  abstraction  of  heat  from  nearby 
articles,  It  is  not  surprising  to  find  the  accepted  standard 
unit  for  expressing  refrigeration  capacities  referred  to  the 
refrigerating  effect  of  a  known  quantity  of  ice.  In  fact, 
since  the  latent  heat  of  fusion  of  ice  is  a  constant,  this 
furnishes  an  excellent  [basis  for  estimating  refrigeration. 
The  generally  accepted  unit  of  measure  is  the  ton  of  refrigera- 
tion, which  may  'be  defined  as  tltc  amount  of  heat  (B,  t.  u.)  which 
one  ton  of  2000  pounds  of  ice  at  32  degrees,  will  o&sorft  in  meJtinfi  to 
tenter  at  32  degrees.  iSince  the  latent  iheat  of  ice  is  144  B.  t.  u. 
per  pound,  one  to.n  of  'refrigeration  is  equal  to  288000  B.  t.  u. 
Just  as  a  pumping  plant  is  .rated  at -a  certain,  number  of 
millions  of  'gallons,  meaning  millions  of  gallons  in  twenty- 
fO'ur  -hours,  so  a  refrigeration  plant  is  rated  in  so  many 
tons  of  refrigeration,  meaning  so  many  tons  in  twenty-four 
•hours.  Hence  one  ton  of  refrigeration  capacity  for  one  day 
is  equivalent  to  12000  B.  t.  u.  per  .'hour,  this  value  being  tJic 
unit  of  refrigerating  capacity,  sometimes  referred  to  as  tonnage 
capacity,  or  refrigerating  effect,  and  usually  designated  by  T. 

211.  Calculation    of    Required     Capacity: — To     estimate 
closely    the    tonnage   capacity    of   a    refrigerating    plant    for 
any  certain  store  space  requires  specific  attention  to  supply- 
ing the  folHowing  losses: 

(a)  The  radiated  and  conducted  'heat  entering  the 
room.  This  may  -be  divided  into  that  due  to  the  walls  and 
that  due  to  the  windows  and  isky-lights. 

:(ib)  The  ih>eat  entering  iby  the  .renewal  of  the  air,  or 
ventilation  of  the  enclosed  space.  This  may  be  divided  into 
heat  .given  off  by  the  air  and  <heat  given  off  due  to  the 
latent  .heat  of  the  moisture. 

(c)     The  -heat  entering  by  the  opening  of  doors. 

'(<!)  The  heat  from  the  men  at  work,  lights,  chemical 
fermentation  processes,  etc. 

(e)     iThe  .heat  abstracted  from  material  in  cold  storage. 

'Refrigeration  losses  due  to  entrance  of  radiated  and  con- 
ducted heat  may  ,be  calculated  by  formulas  10,  11  and  12, 


REFRIGERATION 


309 


Chapter  III,  if  the  proper  transmission  constants  are  in- 
serted. To  obtain  these  constants  for  various  types  of  in- 
sulation use  Tables  IV  and  XXIX. 


TABLE  XXIX. 
Heat  Transmission  of  Standard  Types  of  Dry  Insulation. 


Material 

K 

Material 

K 

Mill 
1" 

shaving's,  Type  (a) 
thickness 

1330 

Hair  Felt,  Type  (a) 
1"  thickness  . 

.138 

1090 

%",   %",   1/4"  Type  (c) 

105 

3' 

„ 

.0920 

Sheet  Cork,  Type  (d) 

*  .  •**  -  1 

.0800 

4"  with  1"  air  space 

.050 

5" 

,< 

0710 

5"  with  1"  air  space 

.037 

6" 

„ 

.0630 

3",  Type  (b)   ' 

.087 

7" 

„ 

.0570 

1",  Type  (a)   

.137 

8" 

M 

.0520 

Granulated  Cork 

10" 

„ 

0440 

4",  Type  (a)   

.071 

12" 

M 

.0390 

Mineral  Wool 

14" 

« 

.0340 

2%",  Type  (b)   

.151 

16" 

„ 

0308 

1",  Type  (b) 

.192 

IS" 

., 

.0279 

Air  Spaces 

20" 

M 

0255 

8",  Type  (a)   

.112 

?,?," 

„ 

0235 

24" 

" 

.0218 

TAR   PAPER - 
/    SHAVINGS^ 


JAR  RAPE  I 


In  general  any  space  to  be  kept  at  or  below  zero  degrees 
should  have  insulation  allowing  no  greater  transmission 
than  .04,  and  for  spaces  to  be  kept  at  from  0  degrees  to  30 


310  HEATING    AND    VENTILATION 

degrees  no  greater  transmission  should  be  allowed  than  .06, 
while  for  temperatures  above  30  degrees  a  transmission  as 
great  as  .1  is  allowable.  In  any  case,  however,  it  should  be 
remembered  that  the  heat  loss,  and  therefore  the  expense  of 
operation,  is  directly  proportional  to  this  factor  and  the 
best  possible  insulation,  consistent  with  available  building- 
funds,  is  the  one  to  use,  the  ceiling  and  floor  being  as  care- 
fully insulated  as  the  walls.  Window  construction  should 
be  tight,  non-opening,  and  at  least  double. 

The  refrigeration  loss  due  to  ventilation  may  be  considered 
under  two  heads,  i.  e.,  the  cooling  of  the  air  from  the 
higher  to  the  lower  temperature,  and  the  cooling1,  condens- 
ing and  freezing  of  the  moisture  in  the  air.  In  this  par- 
ticular, air  cooling  cannot  be  considered  exactly  the  re- 
verse of  air  warming.  In  air  warming  the  vapor  present 
absorbs  heat  but  this  vapor  has  so  little  heat  capacity  com- 
pared with  that  of  the  air  that  no  noteworthy  error  is  intro- 
duced by  ignoring  the  vapor.  However,  in  air  cooling  the 
dew  point  is  almost  invariably  reached  and  passed,  so  that 
considerable  moisture  is  changed  from  the  vapor  to  the 
liquid  with  a  liberation  of  its  heat  of  vaporization.  This  is 
considerable  and  cannot  be  ignored  without  serious  error. 
If,  farther,  conditions  are  such  that  this  moisture  is  frozen, 
its  latent  heat  of  freezing  must  also  be  accounted  for. 
These  two  items  are  relatively  so  large  that  to  cool  air 
through  a  given  range  of  temperature  may  involve  several 
times  the  heat  transfer  required  to  warm  the  same  air 
through  the  same  range  of  temperature. 

APPLICATION. — Assume  outside  air  95  degrees,  relative 
humidity  85  per  cent.,  temperature  of  air  upon  leaving  cool- 
ing coils  30  degrees  and  temperature  of  coil  surface  10  de- 
grees. If  180000  cubic  feet  of  air  per  hour  are  drawn  in 
from  the  atmosphere,  the  refrigerating  capacity  of  the  coils 
may  be  obtained  as  follows.  To  cool  the  air  from  95  degrees 
to  30  degrees  will  require  (formula  9), 

180000   X    (95  —  30) 

=212700  B.  t.  u. 


55 

At  95  degrees  and  85  per  cent,  humidity  one  cubic  foot  of 
air  contains,  (Table  10,  Appendix,)  .85  X  17.124  =  14.555 
grains  of  moisture.  At  30  degrees  and  saturation  one  cubic 


REFRIGERATION.  311 

foot  of  air  contains,    (Table  10),   1.935  grains.     Hence  there 

180000  (14.555  —  1.935) 

would  be  deposited  upon  the  coils = 

7000 

324.5    pounds   of   moisture    per   hour.      Now    there    would    be 
absorbed   from   each   pound   of   this   moisture 
32  B.  t.  u.  to  cool  from  95  to  32  degrees. 
1073  B.  t.  u.  to  change  to  liquid  form. 
144  B.  t.  u.  to  freeze  (if  allowed  to  freeze  on  coils). 
11  B.  t.  u.  to  cool  from  32  to  10  degrees. 

1260  B.  t.  u.  total. 

Hence  the  coils  would  have  to  absorb  from  the  moisture 
alone,  1260  X  324.5  =  408870  B.  t.  u.  per  hour,  or  for  both 
moisture  and  air,  212700  +  408870  =  621600  B.  t.  u.  per  hour. 
This  indicates,  for  the  ventilation  proposed,  a  tonnage  capac- 
ity of  621600  -T-  12000  =  51.8  tons  of  refrigeration  needed  at 
the  bunker  room  coilst  The  above  provides  that  the  air  is 
rejected  at  the  interior  temperature,  30  degrees.  Modern 
plants,  however,  would  pre-cool  the  incoming  air  before  it 
reached  the  bunker  room  by  having  part  of  its  heat  ab- 
sorbed by  the  outgoing  30  degree  air,  which  would  reduce 
the  estimate  somewhat  below  51.8  tons. 

In  considering  the  refrigeration  loss  due  to  the  opening  of 
doors  no  rational  method  of  calculation  is  applicable,  but  if 
the  nature  of  the  cold  storage  service  is  such  that  doors  are 
frequently  opened,  as  high  as  25  per  cent,  may  be  allowed. 
Generally  this  is  taken  from  10  to  15  per  cent. 

The  refrigeration  loss  due  to  persons,  lights,  etc.,  may  be 
estimated  as  suggested  in  Art.  31.  If  the  cooling  air  is 
recirculated,  the  cooling  and  freezing  of  the  moisture  given 
off  by  each  person  should  be  taken  into  account,  especially 
if  the  number  is  large.  For  this  purpose  it  is  safe  to  assume 
a  maximum  of  500  grains  of  moisture  given  off  per  person 
per  hour  when  such  persons  are  not  engaged  in  active  phy- 
sical exercise. 

212.  Calculations  for  Square  Feet  of  Cooling  Coll: — This 
problem  presents  greater  uncertainty  in  its  solution  than 
does  the  design  of  a  heating  coil  surface  because  of  the  lack 
of  experimental  data  and  because  of  the  variable  insulat- 
ing effect  of  ice  and  frost  accumulations,  if  allowed  to  form. 
Professor  Hanz  Lorenz  in  "Modern  Refrigerating  Machin- 
ery," page  349,  quotes  4  B.  t.  u.  per  square  foot  per  hour  per 


312  HEATING   AND   VENTILATION 

degree  difference  between  the  average  temperatures  on  the 
inside  and  outside  of  the  coils,  as  a  safe  designing  value 
when  the  air  speed  .is  1000  feet  per  minute  over  the  coils. 
This  is  for  plants  in  continuous  operation,  as  abattoirs,  cold 
stores  and  in  places  where  no  provision  is  made  against  ice 
formation.  For  clean  pipe  surface  in  the  plenum  air  cooling 
plant  of  the  New  York  Stock  Exchange  Building  the  heat 
transmission  is  approximately  430  B.  t.  u.  per  square  foot 
per  hour  with  air  over  coils  at  1000  feet  per  minute.  Under 
the  average  temperatures  there  used,  this  corresponds  to  a 
transmission  per  degree  difference  per  square  focxt  per  hour 
of  approximately  7  B.  t.  u.  These  two  values,  4  and  7,  may 
be  taken  as  about  the  minimum  and  maximum  transmission 
constants  for  plenum  cooling  coil  installations. 

For  direct  cooling  coils,  where  the  pipe  surface  is  sim- 
ply exposed  to  the  air  of  the  room  to  be  cooled,  Lorenz 
recommends  a  transmission  allowance  of  no-t  over  30  B.  t.  u. 
per  square  foot  per  hour,  for  in  such  installations  the  re- 
moval of  ice  and  frost  is  seldom  contemplated.  For  an  aver- 
age room  temperature  of  30  degrees  and  average  brine  tem- 
perature of  10  degrees,  this  would  correspond  to  30  -f-  20  = 
1.5  B.  t.  u.  transmitted  per  square  foot  per  hour  per  degree 
difference. 

APPLICATION  1. — How  many  lineal  feet  of  1%  Inch  direct 
refrigerating  coils  would  be  required  to  keep  a  cold  stor- 
age room  at  30  degrees  if  the  refrigeration  loss  as  80000 
B.  t.  u.  per  hour  total  and  the  temperatures  of  the  brine  en- 
tering and  leaving  the  coils  are  10  degrees  and  20  degrees 
respectively?  Average  brine  temperature  =  15  degrees.  Al- 
lowing a  transmission  constant  of  1.5,  formula  30  becomes, 

H 

Rr  = =  —  .0445  H 

1.5  (15  —  30) 

For  this  problem  we  have  .0445  X  80000  =  3500  square  feet, 
or  3500  X  2.3  =  8050  lineal  feet  of  1^4  inch  pipe. 

^APPLICATION  2. — The  cooling  of  180000  cubic  feet  of  air  per 
hour  in  Art.  211  required  the  extraction  of  621600  B.  t.  u.  per 
hour.  Determine  the  plenum  cooling  surface  required,  if 
brine  enters  at  0  degrees  and  leaves  at  20  degrees. 

Average  brine  temperature  =  10  degrees.  Assuming 
that  there  is  provision  for  1'oeping  coils  clear  of  ice,  and 


REFRIGERATION  313 

hence    a    transmission    constant    of    7    B.    t.    u.    is    allowable, 
formula  42  gives 

621600 

Rr  = =  —  1691  square  feet  of  surface. 

95  +  30 
10 


/ 

7( 


The  negative  sign  indicates  a  flow  of  heat  in  the  direc- 
tion opposite  to  the  flow  in  heating  installations,  for  which 
the  formula  was  primarily  designed. 

213.  General  Application: — Considering  the  school  build- 
ing and  the  table  of  calculated  results  on  pages  202  to  205 
what  amount  of  cooling  coil  surface  would  be  required  to 
keep  the  temperature  of  all  rooms  of  this  building  at  73 
degrees  on  a  day  when  the  outside  air  temperature  is  95 
degrees  and  the  relative  humidity  85  per  cent.? 

Data  Table  XXV  gives  the  total  heat  loss  of  the  three 
floors  of  this  building  as  1483250  B.  t.  u.  per  hour  on  a  zero 
day  when  the  rooms  are  kept  at  70  degrees.  Now  this  same 
building  under  the  summer  conditions  would  have  delivered 
to  it  heat  due  to  a  temperature  difference  of  95  degrees  —  73 
degrees  =  22  degrees.  Hence  the  total  refrigeration  loss  dur- 

22 

ing  the  summer  day  would  be  approximately X  1483250  = 

70 

466000  B.  t.  u.  per  hour,  which  amount  of  heat  would  be  used 
to  warm  the  incoming  air  from  some  temperature  up  to  73 
degrees.  Suppose  the  ventilation  requirement  of  the  build- 
Ing  is  2000000  cubic  feet  per  hour.  Since  it  requires  ^  of 
a  B.  t  u.  to  warm  one  cubic  foot  of  air  one  degree,  [2000000 
(73  _  f>]  4.  55  —  466000,  or  t  =  60.2,  say  60  degrees.  (See 
Arts.  36  and  38  and  observe  that  the  second  term  of  the  right 
hand  member  of  formula  17  becomes  a  negative  term). 

While  ,the  air  is  traversing  the  ducts  between  the  coils 
and  the  rooms,  allow  a  rise  in  temperature  of  5  degrees. 
The  coils  would  then  be  required  to  deliver  2000000  cubic 
feet  of  air  per  hour  a,t  55  degrees  when  supplied  wlith  air  at 
90  degrees  and  85  per  cent,  humidity.  To  cool  'this  amount 
of  air  through  the  given  range  would  require  the  absorption 
of  (formula  9),  [2000000  X  (95  —  55)]  -j-  55  =  1454500  B.  t.  u. 
At  95  degrees  and  85  per  cent,  humidity,  1  cubic  foot  of  air 
contains  (Table  10),  .85  X  17.124  =  14.555  grains  of  moisture. 
At  55  degrees  >and  saturation  point,  1  cubic  foot  of  air  con- 
tains (Table  10),  4.849  grains  of  moisture.  Hence,  neglecting 


314  HEATING    AND    VENTILATION 

change  in  air  volume,  there  would  be  deposited  on  the  coils 
approximately  [2000000  (14.555  —  4.849)]  -^  7000  =  2775 
pounds  of  moisture  per  hour. 

Now,  if  an  average  brine  temperature  of  10  degrees  is 
used  and  provision  is  made  for  keeping  the  coils  clear  of  ice, 
the  condensation  will  leave  at  some  temperature  above  10 
degrees,  say  20  degrees,  and  there  will  be  absorbed  from 
each  pound  of  this  moisture  approximately 

20  B.  t.  u.  to  cool  from  95  to  55  degrees. 

1061  B.   t.   u.   to   change  to  liquid  form  at  55  degrees. 
35  B.  t.  u.  to  cool  the  water  from  55  to  20  degrees. 

1116  B.  t.   u.  total. 

Hence  the  coils  would  have  to  absorb  from  moisture  alone, 
2775  X  1116  =  3096900  B.  t.  u.,  or  from  both  moisture  and  air 
a  total  of  1454500  +  3096900  =  4551400  B.  t.  u.  per  hour.  At 
an  allowed  rate  of  transmission  of  7  B.  t.  u.  there  would  be 
required  to  cool  this  building  a  total  of  approximately  9100 
square  feet  of  coil  surface,  under  the  conditions  of  ventila- 
tion as  assumed. 

It  should  be  noted  that  whereas  only  3000  square  feet 
of  plenum  surface  were  sufficient  to  heat  the  building  ac- 
cording to  Application  2,  Art.  115,  it  requires  fully  three 
times  this  amount  of  surface  in  cooling  coils  to  cool  the 
building  under  the  assumed  conditions.  Upon  inspection  it 
is  seen  that  the  greatest  work  of  the  cooling  coils  is  the 
condensation  and  cooling  of  the  moisture. 

The  relative  humidity  within  the  cooled  rooms  would  b? 
approximately  55  per  cent.,  for  the  content  per  cubic  foot  of 
incoming  air  is  4.849  grains,  and  the  capacity  of  the  air 
when  heated  to  73  degrees  is  8.782  grains  showing  a  relative 

4.849 
humidity,  after  heating,  of =  55  per  cent.     This  would 

8.782 

be  raised  somewhat  by  the  persons  present. 

214.  Ice  Making  Capacity.  Calculation: — Neglecting 
losses,  the  ice  making  capacity  of  a  refrigerating  plant  for 
a  certain  refrigeration  tonnage  may  be  expressed 

144  T 

I  =  (107) 

(t  —  32)  +  144  +  .5  (32  —  *x) 

in  which  7  =  tons  of  ice  produced  per  24  hours,  T  =  refrig- 


REFRIGERATION  315 

eration  tonnage  or  rating  of  plant,  *  =  initial  temperature  of 
water  and  <i  =  final  temperature  of  ice,  usually  12  to  18 
degrees. 

APPLICATION.  —  What  should  be  the  ice  making  capacity  of 
a  plant  having  a  tonnage  rating  of  100,  if  *  =  70  degrees  and 
ti  =  16  degrees?  Take  losses  at  35  per  cent. 

.65  X  144  X  100 

I  =  •  -  =  49.3  tons  in  24  hours. 
(70  —  32)  -f  144  +  .5  (32  —  16) 

215.  Gallon  Degree  Calculation:  —  For  use  in  plants  pro- 
ducing ice  by  brine  circulation  a  unit  called  the  gallon  degree 
is  sometimes  used.  It  represents  a  change  of  one  degree 
temperature  in  1  gallon  of  brine  in  one  minute  of  time. 
It  is  not  a  fixed  unit  representing  a  constant  num- 
ber of  B.  t.  u.,  since  the  brine  strength,  and  therefore  its 
specific  heat,  may  vary.  The  value  in  B.  t.  u.  per  minute,  of 
a  gallon  degree  for  any  plant  may  be  obtained  by  multiply- 
ing the  specific  gravity  of  the  brine  by  its  specific  heat  and 
by  8.35,  the  weight  of  one  gallon  of  water,  or  as  a  formula 
may  be  stated 

D  =  8.35  gh  (108) 

where  D  =  B.  t.  u.  per  minute  equal  to  one  gallon  degree, 
g  =  specific  gravity  of  brine  and  h  =  specific  heat  of  brine. 
The  number  of  gallon  degrees  per  ton  of  refrigerating  capacity  may 
be  found  by  dividing  200  by  D,  since  one  ton  of  refrigerating 
capacity  is  equal  to  200  B.  t.  u.  per  minute,  then 

200  24 

Dt  =  -  =  -  for  all  practical  purposes.      (109) 
8.35  gh  gh 

The  refrigerating  capacity  of  a  given  brine  circulation  may  be 
obtained  by  dividing  the  product  of  the  gallons  circulated 
and  the  rise  in  brine  temperature  by  the  value  Dt.  Stated 
as  a  formula  this  is 


T  —  --  =  -  (110) 

Dt  24 

where    T  —   tonnage   capacity,    O   =   gallons    of    brine    circu- 

lated per  minute  and   (t2  —  t3)  =  rise  of  brine  temperature. 

21G.     Refrigerating  Capacity  of  Brine   Cooled  System:  — 

To  calculate  the  capacity  but  two  things  are  required,  the 
amount  of  brine  circulated,  and  the  rise  in  temperature  of 
the  brine.  From  these  the  capacity  may  be  obtained  by 
the  formula 


31 G  HEATING    AND    VENTILATION 

W  h   (tz  —  t3) 

T  = -   (111) 

12000 

where  T  =  tonnage  capacity,  W  =  weight  of  brine  circulated, 
in  pounds,  h  —  specific  heat  of  brine  and  (t2  —  ts)  =  rise  in 
temperature  of  brine. 

217.  Cost  of  Ice  Making  and  Refrigeration: — The  cost  of 
ice  manufacture  is  affected  principally  by  the  following 
items:  price  and  kind  of  fuel,  kind  of  water,  cost  of  labor, 
regularity  of  operation,  method  of  estimating  costs,  etc. 
It  is  found  in  practice  to  range  anywhere  from  $0.50  to 
$2.50  per  ton.  The  items  making  up  the  cost  of  ice.  manu- 
facture are:  fuel  for  power,  labor  at  the  plant,  water,  am- 
monia and  minor  supplies,  maintenance  of  the  plant,  inter- 
est and  taxes,  and  administration.  Mr.  J.  E.  Siebel  in  his 
"Compend  of  Mechanical  Refrigeration  and  Engineering" 
gives  an  itemized  account  of  the  daily  operating  expense  of 
a  100-ton  plant  with  which  he  was  connected,  the  plant 
operating  24  hours  per  day. 

Chief  engineer . .  $     5.00 

Assistant  engineers   6.00 

Firemen    4.00 

Helpers     5.00 

Ice  pullers 9.00 

Expenses    12.00 

Coal  at  $1.10  per  ton   18.00 

Delivery  (wholesale)  50c  per  ton 50.00 

Repairs,  etc 3.00 

Insurance,   taxes,   etc 6.00 

Interest  on  capital   20.55 


Total  for  100  tons  of  ice $138.55 

The  length  of  time  that  the  ice  i?  permitted  to  freeze 
is  a  factor  affecting  the  cost  of  production.  The  following 
figures  are  given  for  a  10-ton  plant: 

Ten  tons  Ten  tons 

in  12  hours  in  24  hours 

Engineer   $2.50  $   5.00 

Fireman 1.50  3.00 

Tankmen,  helpers  .  .            1.50  3.00 

Coal     3.00  3.00 

Repairs,  supplies,  etc.          1.50  1.50 


Total    for    10    tons       '$10.00  $15.50 


REFRIGERATION  317 

Mr.  A.  P.  Criswell,  in  "Ice  and  Refrigeration,"  gives  the 
following  approximate  costs  for  the  production  of  can  ice 
per  ton  with  coal  at  $2.50  per  ton  and  with  a  simple  distill- 
ing system.  The  figures  are  for  the  plant  operating  at  full 
capacity  and  do  not  include  cost  of  administration. 

Capacity  of  plant                                            Cost  per  ton 

10  tons    $1.58 

20     "        1.48 

30     "         1.42 

40      " 1.38 

50      "         1.36 

70     "         1.34 

100     ?•:•  • . 1.34 

120      " 1.30 

Mr.  Karl  W-egemann  states  that  a  certain  moderate  sized 
plant  of  the  absorption  system  produced  ice  for  a  number 
of  years  a,t  an  average  cost  of  $0.85  per  ton  after  allowing 
for  melting  and  breakage.  This  included  all  charges  ex- 
cept for  interest,  insurance  and  administration. 

The  following  figures  taken  from  the  books  of  another 
plant  show  clearly  the  effect  of  demand  upon  the  cost  of 
manufacture. 

Month  Cost  per  ton 

January    $3.50 

February    3.70 

March    2.80 

April 2.17 

May 1.75 

June     1.19 

July    1.02 

August    1.02 

September    1.03 

October 1.26 

November     2.10 

December     ,  2.94 


318  HEATING    AND    VENTILATION 


REFERENCES. 
Reference*   on   Refrigeration. 

TECHNICAL   BOOKS. 

A.  J.  Wallis-Taylor,  Pocket-Book  of  Refrigeration.  John 
Wemyss  Anderson,  Refrigeration.  James  Alfred  Ewing,  Mechan- 
ical Refrigeration.  J.  E.  Siebel,  Compend  of  Mechanical  Refriger- 
ation. International  Library  of  Technology,  pp.  643-966.  I.  C  S 
Pamphlets,  1238  A,  1238  B,  1238  C,  1240,  1241,  1242,  1243, 
1246  A,  1246  B,  1247  and  1250.  American  School  of  Corre- 
spondence; Refrigeration,  Dickerman  &  Boyer;  Refrigeration,  Mil- 
ton W.  Arrowwood. 

TECHNICAL  PERIODICALS. 

Ice  and  Refrigeration.  The  Ice  Factory  of  the  Future,  Vic- 
tor H.  Becker,  Jan.  1910.  Cell  Box  System  for  Making  Raw 
Water  Ice,  A.  C.  Bishop,  Dec.  1909.  The  P'looded  System,  H. 
Rassbach,  Jan.  1910.  Baker  Chocolate  Cooling  Plant,  Aug. 
1910.  The  Working  Fluid  in  Refrigeration,  H.  J.  Maclntyre, 
Nov.  1910.  Sulphur  Dioxide  as  Refrigerating  Agent,  W.  S. 
Douglas,  Oct.  1911.  Dry  Blast  Refrigeration,  Nov.  1912. 
Power,  Artificial  Systems  of  Refrigeration,  C.  P.  Wood,  May 

3,  1910.     Mechanical  Refrigeration,    F.   E.  Matthews,  Aug.   9, 
1910.      Elements    of    Compression    System,    F.    E.    Matthews, 
Sept.   6,   1910.     Can  and  Plate  Systems  of  Making  Ice,   F.   E. 
Matthews,  Mar.  14,  1911.     Cold  Storage  of  Furs  and  Fabrics, 
E.   F.    Tweedy,   Feb.   20,   1912.     Ammonia   Absorption   Refrig- 
eration System,  Fred  Ophuls.  Apr.  23,  1912.     Central  Refrig- 
erating Plant  at  Atlanta,  Georgia.  May  7.  1912.     Pre-Cooling 
Plant  of  Southern   Pacific  Railway,   LeRoy  W.  Allison,   June 

4,  1912.     Cooling  Air  of  Buildings  by  Mechanical  Refrigera- 
tion, E.  F.  Tweedy,  Nov.  28,  1911.     Electrical  World.     Ice  Mak- 
ing from  Exhaust  Steam,  Apr.   7,  1910. 


CHAPTER  XVIII. 


PLANS    AND    SPECIFICATIONS    FOR    HEATING    SYSTEMS. 


218.  In  Planning  for  and  Executing  Engineering  Con- 
tracts, the  responsibilities  assumed  by  the  various  interested 
parties  should  be  thoroughly  studied.  The  following  outline 
shows  the  relationship  between  these  parties  and  the  order 
of  the  responsibility. 
Owner  Engineer. 

Superintendent  and  Inspector. 

Purcha  General  contractor,  Subcontractors,  Foremen  and 

Workmen. 

The  engineer,  the  superintendent  and  the  general  con- 
tractor occupy  positions  of  like  responsibility  with  relation 
to  the  purchaser.  The  first  two  work  for  the  interest  of  the 
purchaser  to  obtain  the  best  possible  results  for  the  least 
money,  and  the  last  endeavors  to  fulfill  the  contract  to  the 
satisfaction  of  the  superintendent,  at  the  least  possible  ex- 
pense to  himself.  These  points  of  view  are  quite  different 
and  sometimes  are  antagonistic,  but  both  are  right  and  just. 
Of  the  three  parties,  the  engineer  has  the  greatest  respon- 
sibility. It  is  his  duty  to  draw  up  the  plans  and  to  write 
the  specifications  in  such  a  way  that  every  point  is  made 
clear  and  that  no  question  of  dispute  may  arise  between  the 
superintendent  and  the  contractor.  His  plans  should  detail 
every  part  of  the  design  with  full  notes.  His  specifications 
should  explain  all  points  that  are  difficult  to  delineate  on  the 
plans.  They  should  give  the  purchaser's  views  covering  all 
preferences,  and  should  definitely  state  where  and  what  ma- 
terials may  be  substituted.  Where  any  point  is  not  definitely 
settled  and  left  to  the  judgment  of  the  •contractor,  he  may 
be  expected  to  interpret  this  point  in  his  favor  and  use  the 
cheapest  material  that  in  his  judgment  will  give  good  re- 
sults. This  opinion  may  differ  from  that  held  by  the  pur- 
chaser. All  parts  should  be  made  so  plain  that  no  two  opin- 
ions could  be  had  on  any  important  point.  The  engineer 
should  also  be  careful  that  the  plans  and  specifications  agree 
in  every  part.  The  inspector  is  the  superintendent's  repre- 
sentative on  the  grounds  and  is  supposed  to  inspect  and 
pass  upon  all  materials  delivered  on  the  grounds,  and  the 


320  HEATING    AND    VENTILATION 

quality  of  workmanship  in  installing.  For  such  information 
see  Byrne's  "Inspector's  Pocket-Book."  The  general  con- 
tractor usually  sublets  parts  of  the  contract  to  subcon- 
tractors who  work  through  the  foreman  and  workmen  to 
finish  the  work  upon  the  same  basis  as  the  general  con- 
tractor. 

The  following  brief  set  of  specifications  are  not  con- 
sidered complete  but  are  merely  inserted  to  suggest  how 
such  work  is  done. 

Typical   Specification!*. 

TITLE  PAGE: — 

SPECIFICATIONS 

for  the 

MATERIALS   AND    WORKMANSHIP 
Required  to   Install 


(Type  of  system) 

HEATING  AND  VENTILATING  SYSTEM 
in  the 

(Building) 


(Location) 
by 


(Name   of  designer) 
INDEX  PAGE: — 

(To  be   compiled  after  the  specifications  are  written.) 

General   Remarks    to    Contractor. — In    the    following    specifi- 
cations, all  -references  to  the  Owner  or  Purchaser  will  mean 

or  any  person  or  persons  delegated  by 

to  serve  as  the  representative.     The  S»//>rr- 

intendcnt  of  Ituildings  will  be  the  purchaser's  representative  at 
all  times,  unless  otherwise  definitely  stated.  The  contractor 
will,  therefore,  refer  all  doubtful  questions  or  misunder- 


TYPICAL    SPECIFICATIONS  321 

standings,  if  any,  to  the  superintendent,  whose  decision  will 
be  final.  In  case  of  any  doubt  concerning  the  meaning  of 
any  part  of  the  plans  or  specifications,  the  contractor  shall 
obtain  definite  interpretation  from  the  superintendent  be- 
fore proceeding  with  the  work. 

These  specifications  with  the  accompanying  plans  and 
details  (sheets  ....  to  ....  inclusive)  cover  the  purchase  of 
all  the  materials  as  specified  later  (the  s-ame  materials  to 
be  new  in  every  case),  and  the  installation  of  the  same  in  a 
first  class  manner  within  the  above  named  building,  located 
at (street)  (city)  (state). 

It  will  be  understood  that  the  successful  bidder,  herein- 
after called  the  contractor,  shall  work  in  conformity  with 
these  plans  and  specifications  and  shall,  to  the  best  of  his 
ability,  carry  out  their  true  intent  and  meaning.  He  shall 
purchase  and  erect  all  materials  and  apparatus  required  to 
make  the  above  system  complete  in  all  its  parts,  supplying 
only  such  quality  >of  materials  and  workmanship  as  will  har- 
monize with  -a  first  class  system  and  develop  satisfactory 
results  when  working  under  the  .heaviest  service  to  which 
such  plants  are  subjected. 

The  contractor  shall  lay  out  his  own  work  and  be  re- 
sponsible for  its  fitting  to  place.  He  shall  keep  a  competent 
foreman  on  the  grounds  and  shall  properly  protect  his  work 
at  all  times,  making  good  any  damage  that  may  come  to  it, 
or  to  the  building,  or  to  the  work  of  other  contractors  from 
any  source  whatsoever,  which  may  be  chargeable  to  himself 
•or  to  his  employees  in  the  course  of  their  operations. 

Any  defects  in  materials  or  workmanship,  other  than 
as  stated  under — (state  exceptions  if  any) — that  may  develop 
within  one  year,  shall  be  made  good  by  the  contractor  upon 
written  notification  from  the  purchaser  without  additional 
cost  to  the  purchaser. 

The  contractor  shall,  wherever  it  is  found  necessary, 
make  all  excavations  and  back-fill  to  the  satisfaction  of  the 
superintendent. 

The  contractor  shall  be  responsible  for  all  cuttings  of 
wood  work,  brick  work  or  cement  work,  found  necessary 
in  fitting  his  materials  to  place,  either  within  or  without  the 
building;  the  cutting  to  be  done  to  the  satisfaction  of  the 
superintendent.  The  contractor  shall  be  required  to  connect 
and  supply  water  and  gas  for  building  purposes,  and  shall 


322  HEATING    AND    VENTILATION 

assume  all  responsibility  for  the  same. 

The  contractor  shall  be  required  to  protect  the  purchaser 
from  damage  suits,  originating  from  personal  injuries  re- 
ceived during  the  progress  of  the  work;  also,  from  actions 
at  law  because  of  the  use  of  patented  articles  furnished  by 
the  contractor;  also,  from  any  lien  or  liens  arising  because 
of  any  materials  or  labor  furnished. 

The  purchaser  reserves  the  right  to  reject  any  or  all 
bids. 

No  changes  in  these  plans  and  specifications  will  be 
allowed  except  upon  written  agreement  signed  by  both  the 
contractor  and  the  purchaser's  representative. 

System. — Specify  the  system  of  heating  in  a  general  way; 
high  pressure,  low  pressure  or  vacuum;  direct,  direct-indi- 
rect or  indirect  radiation;  basement  or  attic  mains;  one 
or  two-pipe  connections  to  radiators.  If  ventilation  is 
provided,  state  the  movement  of  the  air  and  the  general 
arrangement  of  fans,  coils  or  other  heating  surfaces.  Single 
or  double  duct  air  lines,  etc. 

Boilers. — Specify  type,  number,  size  and  capacity,  steam, 
pressure,  approximate  horse-power,  heating  surface,  grate 
surface  and  kind  of  coal  to  be  used.  Locate  on  plan  and  ele- 
vation. Explain  method  of  setting,  portable  or  brick. 
Specify  also,  flue  connection,  heating  and  water  pipe  con- 
nections,  kind  of  grate,  thermometers,  gages,  automatic 
damper  connection,  firing  tools  and  conditions  of  final  tests. 

Conduits  and  Conduit  Mains. — (In  this  it  is  assumed  that  the 
boilers  are  not  within  the  building).  In  addition  to  the  lay- 
out, give  sections  of  the  conduit  on  plans  showing  method 
of  construction,  supporting  and  insulating  pipes,  and  drain- 
age of  pipes  and  conduits.  Specify  quality  and  size  of  mate- 
rials, pitch  and  drainage  of  pipes  and  all  other  points  not 
specially  provided  for  in  the  plans. 

Anchors. — Locate  and  draw  on  plans  and  specify  for  the 
installation  regarding  quality  of  materials. 

Expansion  Joints  or  Take-ups. — Locate  and  draw  on  plans. 
Select  type  of  joint  and  specify  for  amount  of  safe  take-up 
and  for  quality  of  material. 

Mains  and  Returns. — Trace  the  steam  from  the  point  where 
it  enters  the  main,  through  all  the  special  fittings  of  the 

system.  Show  where  the  condensation  is  dripped 

to  the  returns  through  traps  or  separating  devices.  Specify 


TYPICAL    SPECIFICATIONS  323 

amount  and  direction  of  pitch,  kind  of  fittings  (flanged  or 
screwed,  cast  iron  or  malleable  iron),  kind  of  corners  (long 
or  short),  method  of  taking  up  expansion,  and  contraction. 
Trace  returns  and  specify  dry  or  wet. 

Branches  to  Risers. — Take  branches  from  top  of  mains  by 
tees,  short  nipples  and  ells,  and  enter  the  bottom  of  the 
risers  by  sufficient  inclination  to  give  good  drainage. 

Risers. — Locate  risers  according  to  plan.  They  shall  be 
straight  and  plumb  and  shall  conform  to  the  sizes  given  on 
the  plans.  No  riser  shall  overlap  the  casing  around  win- 
dows. State  how  branches  are  to  be  taken  off  leading  to 
radiators,  relative  to  the  ceiling  or  floor. 

Radiator  Connections. — Specify,  one-pipe  or  two-pipe,  num- 
ber and  kind  of  valves,  sizes  of  connections  and  hand  or 
automatic  control.  All  connections  shall  allow  for  good 
drainage  and  expansion.  Distinguish  between  wall  radiator 
and  floor  radiator  connections.  If  automatic  control  is  used, 
hand  valves  at  the  radiators  are  usually  omitted. 

Radiators. — Specify  floor  or  wall  radiators,  with  type, 
height,  number  of  columns  and  number  of  sections.  If  other 
radiators  are  substituted  for  the  ones  that  are  referred  to 
as  acceptable,  they  must  be  of  equal  amount  of  surface  and 
acceptable  to  the  superintendent.  Specify  brackets  for  wall 
radiators,  also,  air  valves  for  all  radiators,  stating  type 
and  location  on  the  radiator.  Require  all  radiators  to  be 
cleaned  with  water  or  steam  at  the  factory  and  plugged  at 
inlet  and  outlet  for  shipment. 

Piping. — Define  quality,  weight  and  material  in  all  mains, 
branches  and  risers.  All  sizes  above  one  and  one-half  inch 
are  usually  lap  welded.  Piping  should  be  stood  on  end  and 
pounded  to  remove  all  scale  before  going  into  the  system. 
All  pipes  1  inch  and  smaller  should  be  reamed  out  full  size 
after  cutting. 

Fittings. — Specify  quality  of  fittings,  whether  light,  stand- 
ard or  heavy,  malleable  or  cast  iron.  Fittings  with  imper- 
fect threads  should  be  rejected. 

Valves. — Specify  type  (globe,  gate  or  check),  whether 
flanged  or  screwed,  rough  or  smooth  body,  cast  iron  or 
brass,  and  give  pressure  to  be  carried.  All  valves  should 
be  located  on  the  plans. 

Expansion  Tank. — Specify  capacity  of  tank  in  gallons,  kind 


324  HEATING    AND    VENTILATION 

of  tank  (square  or  round,  wood  or  steel),  method  of  connect- 
ing up  with  fittings  and  valves,  and  locate  definitely  on  plan 
and  elevation.  Connect  also  to  fresh  water  supply  and  to 
overflow. 

Hangers  and  Ceiling  Plates. — Wall  radiators  and  horizontal 
runs  of  pipe  shall  be  supported  on  suitable  expansion  hang- 
ers or  wall  supports  that  will  permit  of  absolute  freedom  of 
expansion.  Supports  shall  be  placed  ....  feet  centers.  Pipe 
holes  in  concrete  floors  shall  be  thimbled.  Holes  through 
wooden  walls  and  floors  shall  have  suitable  air  space  around 
the  pipe,  and  all  openings  shall  be  covered  with  ornamental 
floor,  ceiling  or  wall  plates. 

Traps. — Specify  type,  size,  capacity  and  location.  State 
whether  flanged  or  screwed  fittings  are  used  and  whether 
by-pass  connection  will  be  pu>t  in.  Refer  to  plans. 

Pressure  Regulating  Talre. — Specify  type,  size  and  location, 
also  maximum  and  minimum  steam  pressure,  with  guaran- 
tee to  operate  under  slight  change  of  pressure.  State  if 
by-pass  should  be  used  and  explain  with  plans. 

Separators. — Specify  type  (horizontal  or  vertical),  also 
size  and  location. 

Automatic  Control. — The  contractor  will  be  held  responsible 
for  (the  installation  of  all  thermostats,  regulator  valves,  air 
compressor,  piping  and  fittings  required  to  equip  all  rooms 
and  halls  with  an  automatic  ....  temperature  control  sys- 
tem. Specify  approximate  location  and  number  of  thermo- 
stats with  the  desired  finish.  Specify  in  a  general  way,  reg- 
ulator valves  on  radiaitors,  quality  of  pipe,  maximum  test 
pressure  for  pipe,  power  for  air  supply  (.hydraulic,  pneu- 
matic, etc.),  and  supply  tank.  All  materials  in  the  tem- 
perature control  system  shall  be  guaranteed  first  class  by 
the  manufacturer  through  the  contractor,  and  the  system 
shall  be  guaranteed  to  give  perfect  control  for  a  period  of 
(two)  years. 

Fans. — Specify  for  direct  connected  or  belt  driven,  right 
or  left  hand,  capacity,  size,  housing,  direction  of  discharge, 
horse-power,  R.  P.  M.  and  pressure.  State  in  a  general  way 
the  requirements  of  the  fan  wheel,  steel  plate  housing,  shaft, 
bearings  and  the  method  of  lubrication. 

Engine. — Specify  type,  horse-power,  steam  pressure,  ap- 
proximate cut-off,  speed  and  kind  of  control. 


TYPICAL    SPECIFICATIONS  325 

Electric  Motors. — Specify  type,  horse-power,  voltage,  cycles, 
phases  and  R.  P.  M. 

Indirect  Heating  Surface. — 'Specify  the  kind  of  surface  to 
be  put  in  and  then  state  the  total  number  of  square  feet 
of  surface,  with  the  width,  height  and  depth  of  the  heater. 
Staite  definitely  how  the  heaters  will  be  assembled,  giving 
free  height  of  heater  above  the  floor.  Describe  damper  con- 
trol, steam  piping  to  and  from  heater,  housing  around  heater, 
connection  from  cold  air  inlet  to  heater  and  connection  from 
heater  to  fan.  See  plans.  The  contractor  will  usually  follow 
installation  instructions  given  by  the  manufacturers  for  the 
erection  of  the  heater  and  engine,  consequently  the  speci- 
fications should  bear  heavily  only  upon  those  points  which 
may  be  varied  to  suit  any  condition.  All  valves,  piping  and 
fittings  in  this  work  should  be  controlled  by  the  general 
specifications  referring  to  these  parts. 

Foundations. — Specify  materials  and  sizes. 

Air  Ducts,  Stacks  and  Galvanised  Iron  Work. — The  drawings 
should  give  the  layout  of  all  the  air  lines,  giving  connections 
between  the  air  lines  and  the  fan,  and  the  air  lines  and  the 
registers.  Where  these  air  lines  are  below  the  floor,  the 
conduit  construction  should  be  carefully  noted.  All  gal- 
vanized iron  work  should  be  shown  on  the  plans  and  the 
quality  and  weight  should  be  specified.  Air  lines  should 
have  long  radius  turns  at  the  corners. 

Registers. — Specify  height  above  floor,  nominal  size  of 
register,  method  of  fitting  in  wall,  the  finish  of  the  regis- 
ter and  whether  fitted  with  shutters  or  not. 

Protection  and  Covering. — Specify  kind  and  quality  of  pipe 
covering  and  t'he  finish  of  the  surface  of  the  covering.  State 
the  amount  of  space  between  heating  pipes  and  unprotected 
woodwork.  Distinguish  between  pipes  that  are  to  be  covered 
and  those  that  are  to  be  painted.  All  radiators  and  piping 
not  covered  should  be  painted  with  two  coats  of  ....  bronze 
or  other  finish  acceptable  to  the  superintendent. 

Completion. — Require  all  rubbish  removed  from  the  build- 
ing and  immediate  grounds  and  deposited  at  a  definite  place. 


APPENDIX 
I 


GENERAL  TABLES. 
HEATING  AND  VENTILATION. 


Tables  in  body  of  text  are  numbered  in  Roman 
numerals,  those  in  the  Appendixes  are  numbered  in 
Arabic  numerals. 

All  tables  that  are  not  considered  general  are  credited 
and  added  by  permission  of  the  authors. 


327 


TABLE    1. 
Squares,   Cubes,    Square   Roots,    Cube   Roots,    Circles. 


No. 
Diam. 

Square 

Cube 

Sq. 
root 

Cube 
root 

Circle 

Cireumf 

Area 

.1 

.010 

.001 

.316 

.464 

.314 

.00785 

.2 

.040 

.008 

.447 

.585 

.628 

.03146 

.3 

.090 

.027 

.548 

.669 

.942 

.07069 

.4 

.160 

.064 

.633 

.737 

1.257 

.12566 

.5 

.250 

.125 

.707 

.794 

1.570 

.19635 

.6 

.360 

.216 

.775 

.843 

1.885 

.28274 

.7 

.490 

.343 

.837 

.888 

2.200 

.38485 

.8 

.640 

.512 

.894 

.928 

2.513 

.50266 

.9 

.810 

.729 

.949 

.965 

2.830 

.63620 

1.0 

1.000 

1.000 

1.000 

1.000 

3.1416 

.7854 

1.1 

1.210 

1.331 

1.0488 

1.0323 

3.456 

.9503 

1.2 

1.440 

1.730 

1.0955 

1.0627 

3.770 

1.1310 

1.1 

1.690 

2.197 

1.1402 

1.0914 

4.084 

1.3273 

1.4 

1.960 

2.744 

1.1832 

1.1187 

4.398 

1.5394 

1.5 

2.250 

3.375 

1.2247 

1.1447 

4.712 

1.7672 

1.6 

2.560 

4.096 

1.2649 

1.1696 

5.027 

2.0106 

1.7 

2.890 

4.913 

1.3C38 

1.1935 

5.341 

2.2698 

1.8 

3.240 

5.832 

1.3416 

1.2164 

5.655 

2.5447 

1.9 

3.610 

6.859 

1.3784 

1.2386 

5.969 

2.8353 

2.0 

4.000 

8.000 

1.4142 

1.2599 

6.283 

3.1416 

2.1 

4.410 

9.261 

1.4491 

.2806 

6.597 

3.4636 

2.2 

4.840 

10.648 

1.4832 

.3006 

6.912 

3.8013 

2.3 

5.290 

12.167 

1.5166 

.3200 

7.226 

4.1548 

2.4 

5.760 

13.824 

1.5492 

.3389 

7.540 

4.5239 

2.5 

6.250 

15.625 

1.5811 

.3572 

7.854 

4.9087 

2.6 

6.760 

17.576 

1.6125 

.3751 

8.168 

5.3093 

2.7 

7.290 

19.683 

1.6432 

.3925 

8.482. 

5.7256 

2.8 

7.840 

21.952 

1.6733 

.4095 

8.797 

6.1575 

2.9 

8.410 

24.389 

1.7029 

.4260 

9.111 

6.6052 

3.0 

9.000 

27.000 

1.7321 

.4422 

9.425 

7.0688 

3.1 

9.610 

29.791 

1.7607 

.4581 

9.739 

7.5477 

3.2 

10.240 

32.768 

1.7889' 

.4736 

10.053 

8.0425 

3.3 

10.890 

35.937 

1.8166 

.4888 

10.367 

8.5530 

3.4 

11.560 

39.304 

1.8439 

.5037 

10.681 

9.0792 

3.5 

12.250 

42.875 

1.8708 

.5183 

10.996 

9.6211 

3.6 

12.960 

46.656 

1.8974 

.5326 

11.310 

10.179 

3.7 

13.690 

50.653 

1.9235 

.5467 

11.624 

10.752 

3.8 

14.440 

54.872 

1.9494 

.5605 

11.938 

11.341 

3.9 

15.210 

59.319 

1.9748 

.5741 

12.252 

11.946 

.0 

16.000 

64.000 

2.0000 

.5870 

12.566 

12.566 

.1 

16.810 

68.921 

2.0249 

.6005 

12.881 

13.203 

.2 

17.640 

74.058 

2.0494 

.6134 

13.195 

13.854 

.3 

18.490 

79.507 

2.0736 

.6261 

13.509 

14.522 

.4 

19.360 

85.184 

2.0976 

.6386 

13.823 

15.205 

328 


No. 

Diam. 

Square 

Cube 

Sq. 
root 

Cube 
root 

Circle 

Oircumf 

Area 

4.5 

iiO.250 

91.125 

2.1213 

1.6510 

14.137 

15.904 

4.6 

21.160 

97.336 

2.1448 

1.6631 

14.451 

16.619 

4.7 

22.090 

103.823 

2.1680 

1.6751 

14.765 

17.349 

4.8 

23.040 

110.592 

2.1909 

1.6869 

15.080 

18.096 

4.9 

24.010 

117.649 

2.2136 

1.6985 

15.394 

18.859 

5.0 

25.000 

125.000 

2.2361 

1.7100 

15.708 

19.635 

5.1 

26.010 

132.651 

2.2583 

1.7213 

16.022 

20.428 

5.2 

27.040 

140.608 

2.2804 

1.7325 

16.336 

21.237 

5.3 

28.090 

148.877 

2.3022 

1.7435 

16.650 

22.062 

5.4 

29.160 

157.464 

2.3238 

1.7544 

16.965 

22.902 

5.5 

30.250 

166.375 

2.3452 

1.7652 

17.279 

23.758 

5.6 

31.360 

175.616 

2.3664 

1.7760 

17.593 

24.630 

5.7 

32.490 

185.193 

2.3S75 

1.7863 

17.907 

25.518 

5.8 

33.640 

195.112 

2.4083 

1.7967 

18.221 

26.421 

5.9 

34.810 

205.379 

2.4290 

1.8070 

18.536 

27.340 

6.0 

36.000 

216.000 

2.4495 

1.8171 

18.850 

28.274 

6.1 

37.210 

226.981 

2.4698 

1.8272 

19.164 

29.225 

6.2 

38.440 

238.328 

2.4900 

1.8371 

19.478 

30.191 

6.3 

39.690 

250.047 

2.5100 

1.8169 

19.792 

31.173 

6.4 

40.960 

262.144 

2.5298 

1.8566 

20.106 

32.170 

6.5 

42.250 

274.625 

2.5495 

1.8663 

20.420 

33.183 

6.6 

43.560 

287.496 

2.5691 

1.8758 

20.735 

34.212 

6.7 

44.890 

300.763 

2.5884 

1.8852 

21.049 

35.257 

6.8 

46.240 

314.432 

2.6077 

1.8945 

21.363 

36.317 

6.9 

47.610 

328.509 

2.6268 

1.9038 

21.677 

37.393 

7.0 

49.000 

343.000 

2.6458 

1.9129 

21.991 

38.485 

7.1 

50.410 

357.911 

2,6646 

1.9220 

22.305 

39.592 

7.2 

51.840 

373.248 

2.6833 

1.9310 

22.619 

40.715 

7.3 

53.290 

389.017 

2.7019 

1.9399 

22.934 

41.854 

7.4 

54.760 

405.224 

2.7203 

1.9487 

23.248 

43.008 

7.5 

56.250 

421.875 

2.7386 

1.9574 

23.562 

44.179 

7.6 

57.760 

438.976 

2.7568 

1.9661 

23.876 

45.365 

7.7 

59.290 

456.533 

2.7749 

1.9747 

24.190 

46.566 

7.8 

60.840 

474.552 

2.7929 

1.9832 

24.504 

47.784 

7.9 

62.410 

493.039 

2.8107 

1.9916 

24.819 

49.017 

8.0 

64.000 

512.000 

2.8284 

2.0000 

25.133 

50.266 

8.1 

65.610 

531.441 

2.8461 

2.0083 

25.447 

51.530 

8.2 

67.240 

551.468 

2.8636 

2.0165 

25.761 

52.810 

8.3 

68.890 

571.787 

2.8810 

2.0247 

26.075 

54.106 

8.4 

70.560 

592.704 

2.8983 

2.0328 

26.389 

55.418 

8.5 

72.250 

614.125 

2.9155 

2.0408 

26.704 

56.745 

8.6 

73.960 

636.056 

2.9326 

2.0488 

27.018 

58.088 

8.7 

75.690 

658.503 

2.9496 

2.0567 

27.332 

59.447 

8.8 

77.440 

681.473 

2.9665 

2.0646 

27.646 

60.821 

8.9 

79.210 

704.969 

2.9833 

2.0724 

27.960 

62.211 

329 


No. 
Diam. 

Square 

Cube 

Sq. 
root 

Cube 
root 

Circle 

Oirctimf 

Area 

9.0 

81.000 

729.000 

3.0000 

2.0801 

28.274 

63.617 

9.1 

82.810 

753.571 

3.0166 

2.0878 

28.588 

65.039 

9.2 

84.640 

778.688 

3.0332 

2.0954 

28.903 

66.476 

9.3 

86.490 

804.357 

3.0496 

2.1029 

29.217 

67.929 

9.4 

88.360 

830.584 

3.0659 

2.1105 

29.531 

69.398 

9.5 

90.250 

857.375 

3.0822 

2.1179 

29.845 

70.882 

9.6 

92.160 

884.736 

3.0984 

2.1253 

30.159 

72.382 

9.7 

94.090 

912.673 

3.1145 

2.1327 

30.473 

73.898 

9.8 

96.040 

941.192 

3.1305 

2.1400 

30.788 

75.430 

9.9 

98.010 

970.299 

3.1464 

2.1472 

31.102 

76.977 

10 

100.000 

1000.000 

3.1623 

2.1544 

31.416 

78.540 

11 

121.000 

1331.000 

3.3166 

2.2239 

34.558 

95.033 

12 

144.000 

1728.000 

3.4641 

2.2894 

37.699 

113.097 

13 

169.000 

2197.000 

3.6056 

2.3513 

40.841 

132.732 

14 

196.000 

2744.000 

3.7417 

2.4101 

43.982 

153.938 

15 

225.000 

3375.000 

3.8730 

2.4662 

47.124 

176.715 

16 

256.000 

4096.000 

4.0000 

2.5198 

50.265 

201.062 

17 

289.000 

4913.000 

4.1231 

2.5713 

53.407 

226.980 

18 

324.000 

5832.000 

.2426 

2.6207 

56.549 

254.469 

19 

361.000 

6859.000 

.3589 

2.6684 

59.690 

283.529 

20 

400.000 

8000.000 

.4721 

2.7144 

62.832 

314.159 

21 

441.000 

9261.000 

.5826 

2.7589 

65.793 

346.361 

22 

484.000 

10648.000 

.6904 

2.8021 

69.115 

380.133 

23 

529.000 

12167.000 

.7958 

2.8439 

72.257 

415.476 

24 

576.000 

13824.000 

.8990 

2.8845 

75.398 

452.389 

25 

625.000 

15625.000 

5.0000 

2.9241 

78.540 

490.874 

26 

676.000 

17576.000 

5.0990 

2.9625 

81.681 

530.929 

27    . 

729.000 

19683.000 

5.1962 

3.0000 

84.823 

572.555 

28 

784.000 

21952.000 

5.2915 

3.0366 

87.965 

615.752 

29 

841.000 

24389.000 

5.3852 

3.0723 

91.106 

660.520 

30 

900.000 

27000.000 

5.4772 

3.1072 

94.248 

706.858 

31 

961.000 

29791.000 

5.5678 

3.1414 

97.389 

754.768 

32 

1024.000 

32768.000 

5.6569 

3.1748 

100.531 

804.248 

33 

1089.000 

35937.000 

5.7446 

3.2075 

103.673 

855.299 

34 

1156.000 

39304.000 

5.8310 

3.2396 

106.841 

907.920 

35 

1225.000 

42875.000 

5.9161 

3.2710 

109.956 

962.113 

36 

1296.000 

46656.000 

6.0000 

3.3019 

113.097 

1017.88 

37 

1369.000 

50653.000 

6.0827 

3.3322 

116.239 

1075.21 

38 

1444.000 

54872.000 

6.1644 

3.3620 

119.381 

1134.11 

39 

1521.000 

59319.000 

6.2450 

3.3912 

122.522 

1194.59 

40 

1600.000 

64000.000 

6.3246 

3.4200 

125.66 

1256.64 

41 

1681.000 

68921.000 

6.4031 

3.4482 

128.81 

1320.25 

42 

1764.000 

74088.000 

6.4807 

3.4760 

131.95 

1385.44 

43 

1849.000 

79507.000 

6.5574 

3.5034 

135.09 

1452.20 

44 

1936.000 

85184.000 

6.6333 

3.5303 

138.23 

1520.53 

320 


No. 
Diam. 

Square 

Cube 

Sq. 
root 

Cube 
root 

Circle 

Circumf 

Area 

45 

2025.000 

91125.000 

6.7082 

3.5569 

141.37 

1590.43 

46 

2116.000 

97336.000 

6.7823 

3.5830 

144.51 

1661.90 

47 

2209.000 

103823.000 

6.8557 

3.6088 

147.65 

1734.94 

48 

2304.000 

110592.000 

6.9282 

3.6342 

150.80 

1809.56 

49 

2401.000 

117649.000 

7.0000 

3.6593 

153.94 

1885.74 

50 

2500.000 

125000.000 

7.0711 

3.6840 

157.08 

1963.50 

51 

2601.000 

132651.000  • 

7.1414 

3.7084 

160.22 

2042.82 

52 

2704.000 

140608.000 

7.2111 

3.7325 

163.36 

2123.72 

53 

2809.000 

148877.000 

7.2801 

3.7563 

166.50 

2206.18 

54 

2916.000 

157464.000 

7.3485 

3.7798 

169.65 

2290.22 

55 

3025.000 

166375.000 

7.4162 

3.8030 

172.79 

2375.83 

56 

3136.000 

175616.000 

7.4833 

3.8259 

175.93 

2463.01 

57 

3249.000 

185193.000 

7.5498 

3.8485 

179.07 

2551.76 

58 

3364.000 

195112.000 

7.6158 

3.8709 

182.21 

2642.08 

59 

3481.000 

205379.000 

7.6811 

3.8930 

185.35 

2733.97 

60 

3600.000 

216000.000 

7.7460 

3.9149 

188.50 

2827.43 

61 

3721.000 

226981.000 

7.8102 

3.9365 

191.64 

2922.47 

62 

3844.000 

238328.000 

7.8740 

3.9579 

194.78 

3019.07 

63 

3969.000 

250047.000 

7.9373 

3.9791 

197.92 

3117.25 

64 

4096.000 

262144.000 

8.0000 

4.0000 

201.06 

3216.99 

65 

4225.000 

274625.000 

8.0623 

4.0207 

204.20 

3318.31 

66 

4356.000 

287496.000 

8.1240 

4.0412 

207.34 

3421.19 

67 

4489.000 

300763.000 

8.1854 

4.0615 

210.49 

3525.65 

68 

4624.000 

314432.000 

8.2462 

4.0817 

213.63 

3631.68 

69 

4761.000 

328509.000 

8.3066 

4.1016 

216.77 

3739.28 

70 

4900.000 

343000.000 

8.3666 

4.1213 

219.91 

3848.45 

71 

5041.000 

357911.000 

8.4261 

4.1408 

223.05 

3959.19 

72 

5184.000 

373248.000 

8.4853 

4.1602 

226.19 

4071.50 

73 

5329.000 

389017.000 

8.5440 

4.1793 

229.34 

4185.39 

74 

5476.000 

405224.000 

8.6023 

4.1983 

232.48 

4300.84 

75 

5625.000 

421875.000 

8.6603 

4.2172 

235.62 

4417.86 

76 

5776.000 

438976.000 

8.7178 

4.2358 

238.76 

4536.46 

77 

5929.000 

456533.000 

8.7750 

4.2543 

241.90 

4656.63 

78 

6084.000 

474552.000 

8.8318 

4.2727 

245.04 

4778.36 

79 

6241.000 

493039.000 

8.8882 

4.2908 

248.19 

4901.67 

80 

6400.000 

512000.000 

8.9443 

4.3089 

251.33 

5026.55 

81 

6561.000 

531441.000 

9.0000 

4.3267 

254.47 

5153.00 

82 

6724.000 

551368.000 

9.0554 

4.3445 

257.61 

5281.02 

83 

6889.000 

571787.000 

9.1104 

4.3621 

260.75 

5410.61 

84 

7056.000 

592704.000 

9.1652 

4.3795 

263.89 

5541.77 

85 

7225.000 

614125.000 

9.2195 

4.391' 

267.04 

5674.50 

86 

7396.000 

636056.000 

9.2736 

4.4140 

270.18 

5808.80 

87 

7569.000 

658503.000 

9.3274 

4.4310 

273.32 

.     5944.68 

88 

7744.000 

681472.000 

9.3808 

4.4480 

276.46 

6082.12 

89 

7921.000 

704969.000 

9.4340 

4.4647 

279.60 

6221.14 

331 


No. 
Diam. 

Square 

Cube 

Sq. 
root 

Cube 
root 

Circle 

Oircumf 

Area 

90 

8100.000 

729000.000 

9.4868 

4.4814 

282.74 

6361.73 

91 

8281.000 

753571.000 

9.5394 

4.4979 

285.88 

6503.88 

92 

8464.000 

778688.000 

9.5917 

4.5144 

289.03 

6647.61 

93 

8649.000 

804357.000 

9.6437 

4.5307 

292.17 

6792.91 

94 

8836.  000 

830584.000 

9.6954 

4.5468 

295.81 

6939.78 

95 

9025.000 

857375.000 

9.7468 

4.5629 

298.45 

7088.22 

96 

9216.000 

884736.000 

9.7980 

4.5789 

301.59 

7238.23 

97 

9409.000 

912673.000 

9.8489 

4.5947 

304.73 

7389.81 

98 

9604.000 

941192.000 

9.8995 

4.6104 

307.88 

7542.96 

99 

9801.000 

970299.000 

9.9499 

4.6261 

311.02 

7697.69 

100 

10000.000 

1000000.000 

10.0000 

4.6416 

314.16 

7853.98 

105 

11025.000 

1157625.000 

10.2470 

4.7177 

329.87 

8659.01 

110 

12100.000 

1331000.000 

10.4881 

4.7914 

345.58 

9503.32 

115 

13225.000 

1520875.000 

10.7238 

4.8629 

361.28 

10386.89 

120 

14400.000 

1728000.000 

10.9545 

4.9324 

376.99 

11309.73 

125 

15625.000 

1953125.000 

11.1803 

5.0000 

392.70 

12271.85 

130 

16900.000 

2197000.000 

11.4018 

5.0658 

408.41 

13273.23 

135 

18225.000 

2460375.000 

11.6190 

5.1299 

424.12 

14313.88 

140 

19600.000 

2744000.000 

11.8322 

5.1925 

439.82 

15393.80 

145 

21025.000 

3048625.000 

12.0416 

5.2536 

455.53 

16513.00 

150 

22500.000 

3375000.000 

12.2474 

5.3133 

471.24 

17671.46 

155 

24025.000 

3723875.000 

12.4499 

5.3717 

486.95 

18869.19 

160 

25600.  000 

4096000.000 

12.6491 

5.4288 

502.65 

20106.19 

165 

27225.000 

4492125.000 

12.8452 

5.4848 

518.36 

21382.46 

170 

28900.000 

4913000.000 

13.0384 

5.5397 

534.07 

22698.01 

175 

30625.000 

5359375.000 

13.2288 

5.5934 

549.78 

24052.82 

180 

32400.000 

5832000.000 

13.4164 

5.6462 

565.49 

25446.90 

185 

34225.000 

6331625.000 

13.6015 

5.6980 

581.19 

26880.25 

190 

36100.000 

6859000.000 

13.7840 

5.7489 

596.90 

28352.87 

195 

38025.000 

7414875.000 

13.9642 

5.7989 

612.61 

29864.77 

200 

40000.000 

8000000.000 

14.1421 

5.8480 

628.32 

31415.93 

205 

42025.000 

8615125.000 

14  3178 

5.8964 

644.03 

33006.36 

210 

44100.000 

9261000.000 

14.4914 

5.9439 

659.73 

34636.06 

215 

46225.000 

9938375.000 

14.6629 

5.9907 

675.44 

36305.03 

220 

48400.000 

10648000.000 

14.8324 

6.0368 

691.15 

38013.27 

225 

50625.000 

11390625.000 

15.0000 

6.0822 

706.86 

39760.78 

230 

52900.000 

12167000.000 

15.1658 

6.1269 

722.57 

41547.56 

235 

55225.000 

12977875.000 

15.3297 

6.1710 

738.27 

43373.61 

240 

57600.000 

13824000.000 

15.4919 

6.2145 

753.98 

45238.93 

245 

60025.000 

14706125.000 

15.6525 

6.2573 

769.69 

47143.52 

250 

62500.000 

15625000.000 

15.8114 

6.2996 

785.40 

49087.39 

255 

65025.000 

16581375.000 

15.9687 

6.3413 

801.11 

51070.52 

260 

&7600.000 

17576000.000 

16.1245 

6.3825 

816.81 

53092.92 

265 

70225.000 

18609625.000 

16.2788 

6.4232 

832.52 

55154.59 

270 

72900.000 

19683000.000 

16.4317 

6.4633 

848.23 

57255.53 

332 


No. 
Diam. 

Square 

Cube 

Sq. 
root 

Cube 
root 

Circle 

Circumf 

Area 

275 

75625.000 

20796875.000 

16.5831 

6.5030 

863.94 

59395.74 

280 

78400.000 

21952000.000 

16.7332 

6.5421 

879.65 

61575.22 

285 

81225.000 

23149125.000 

16.8819 

0.5808 

895.35 

63793.97 

290 

84100.000 

24389000.000 

17.0294 

6.6191 

911.06 

66051.99 

295 

87025.000 

25672375.000 

17.1756 

6.6569 

926.77 

68349.28 

300 

90000.000 

27000000.000 

17.3205 

6.6943 

942.48 

70685.83 

305 

93025.000 

28372625.000 

17.4642 

6.7313 

958.19 

73061.65 

310 

96100.000 

29791000.000 

17.6068 

6.7679 

973.89 

75476.76 

315 

99225.000 

31255875.000 

17.7482 

6.8041 

989.60 

77931.13 

320 

102400.000 

32768000.000 

17.8885 

6.8399 

1005.31 

80424.77 

325 

105625.000 

34328125.000 

18.0278 

6.8753 

1021.02 

82957.68 

330 

108900.000 

35937000.000 

18.1659 

6.9104 

1036.73 

85529.86 

335 

112225.000 

37595375.000 

18.3030 

6.9451 

1052.43 

88141.31 

340 

115600.000 

39304000.000 

18.4391 

6.9795 

1068.14 

90792.03 

345 

119025.000 

41063625.000 

18.5742 

7.0136 

1083.85 

93482.02 

350 

122500.000 

42875000.000 

18.7083 

7.0473 

1099.56 

96211.23 

355 

12602.3.000 

44738875.000 

18.8414 

7.0807 

1115.27 

98979.80 

360 

129600.000 

46656000.000 

18.9737 

7.1138 

1130.97 

101787.60 

365 

133225.000 

48627125.000 

19.1050 

7.1466 

1146.68 

104634.67 

370 

136900.000 

50653000.000 

19.2354 

7.1791 

1162.39 

107521.01 

375 

140625.000 

52734375.000 

19.3649 

7.2112 

1178.10 

110446.62 

380 

144400.000 

54872000.000 

19.4936 

7.2432 

1193.81 

113411.49 

385 

148225.000 

57066625.000 

19.6214 

7.2748 

1209.51 

116415.  61 

390 

152100.000 

59319000.000 

19.7484 

7.3061 

1225.22 

119459.06 

395 

156025.000 

61629875.000 

19.8746 

7.3372 

1240.93 

122541.75 

400 

160000.000 

64000000.000 

20.0000 

7.3681 

1256.64 

125663.71 

405 

164025.000 

66430125.000 

20.1246 

7.3986 

1272.35 

128824.93 

410 

168100.000 

68921000.000 

20.2485 

7.4290 

1288.05 

132025.43 

415 

172225.000 

71473375.000 

20.3715 

7.4590 

1303.76 

135265.20 

420 

176400.000 

74088000.000 

20.4939 

7.4889 

1319.47 

138544.24 

425 

180625.000 

76765625.000 

20.6155 

7.5185 

1335.18 

141862.54 

430 

184900.000 

79507000.000 

20.7364 

7.5478 

1350.88 

145220.12 

435 

189225.000 

82312875.000 

20.8567 

7.5770 

1366.59 

148616.97 

440 

193600.000 

85184000.000 

20.9762 

7.6059 

1382.30 

152053.08 

445 

198025.000 

88121125.000 

21.0950 

7.6346 

1398.01 

155528.47 

450 

202500.000 

91125000.000 

21.2132 

7.6631 

1413.72 

159043.13 

455 

207025.000 

94196375.000 

21.3307 

7.6914 

1429.42 

162597.05 

460 

211600.000 

97336000.000 

21.4476 

7.7194 

1445.13 

166190.25 

465 

216225.000 

100544625.000 

21.5639 

7.7473 

1460.84 

169822.72 

470 

220900.000 

103823000.000 

21.6795 

7.7750 

1476.55 

173494.45 

475 

225625.000 

107171875.000 

21.7945 

7.8025 

1492.26 

17  7205.  46 

480 

230400.000 

110592000.000 

21.9089 

7.8297 

1507.96 

180955.74 

485 

235225.000 

114084125.000 

22.0227 

7.8568 

1523.67 

184745.28 

490 

240100.000 

117649000.000 

22.1359 

7.8837 

1539.38 

188574.10 

495 

245025.000 

121287375.000 

22.2486 

7.9105 

1555.09 

192442.18 

500 

250000.000 

125000000.000 

22.3607 

7.9370 

1570.80 

196349.54 

333 


TABLE   2. 
Trigonometric  Functions. 


Angle, 
degrees 

Sine 

Tangent 

Angle, 
degrees 

Sine 

Tangent 

0.0 

0.00000 

0.00000 

90.0 

47.5 

0.73728 

1.0913 

42.5 

2.5 

0.04362 

0.04362 

87.5 

50.0 

0.76604 

1.1917 

40.0 

5.0 

0.08716 

0.08749 

85.0 

52.5 

0.79335 

1.3032 

37.5 

7.5 

0.13053 

0.13165 

82.5 

55.0 

0.81915 

1.4281 

35.0 

10.0 

0.17365 

0.17633 

80.0 

57.5 

0.84339 

1.5697 

32.5 

12.5 

0.21644 

0.22169 

77.5 

60.0 

0.86603 

1.7321 

30.0 

15.0 

0.25882 

0.26795 

75.0 

62.5 

0.88701 

1.9210 

27.5 

17.5 

0.30071 

0.31530 

72.5 

65.0 

0.90631 

2.1445 

25.0 

20.0 

0.34202 

0.36397 

70.0 

67.5 

0.92388 

2.4142 

22.5 

22.5 

0.38263 

0.41421 

67.5 

70.0 

0.93969 

2.7474 

20.0 

25.0 

0.42262 

0.46631 

65.0 

72.5 

0.95372 

3.1716 

17.5 

27.5 

0.46175 

0.52057 

62.5 

75.0 

0.96593 

3.7321 

15.0 

30.0 

0.50000 

0.57735 

60.0 

77.5 

0.97630 

4.5107 

12.5 

32.5 

0.53730 

0.63707 

57.5 

80.0 

0.98481 

5.6713 

10.0 

35.0 

0.57358 

0.70021 

55.0 

82.5 

0.99144 

7.5958 

7.5 

37.5 

0.60876 

0.76733 

52.5 

85.0 

0.99619 

11.430 

5.0 

40.0 

0.64279 

0.83910 

50.0 

87.0 

0.99863 

19.081 

3.0 

42.5 

0.67559 

0.91633 

47.5 

88.5 

0.99966 

38.188 

1.5 

45.0 

0.70711 

1.0000 

45.0 

90.0 

1.0000 

Infinite 

0.0 

Cosine 

Cotan- 
gent 

Angle, 
degrees 

Cosine 

Cotan- 
gent 

Angle, 
degrees 

TABLE   3. 
Equivalents    of    Compound    Units. 

r    27.71      in.  of  water  at  62°  F. 

2.0355  in.  of  mercury  at  32°  F. 

1  Ib.  per  sq.  in.  =*(      2.0416  in.  of  mercury  at  62°  F. 

2.3090  ft.  of  water  at  62°  F. 


1784. 


ft.  of  air  at  32°  F. 


1  oz.  per  sq.   in. 

1  in.    of  water  at  62°   F. 

1  in.    of  water  at  32°   F. 


in.  of  mercury  at 


1    ft.     of    air    at 


F. 


0.1276  in.  of  mercury  at  62°  F. 
1.732    in.  of  water  at  62°  F. 

0.03609  Ib.  or  .5574  oz.  per  s.  in. 

5.196     Ibs.  per  sq.  ft. 

0.0736    in.  of  mercury  at  62°  F. 

5.2021     Ibs.  per  sq.  ft. 
0.036125  Ib.  per  sq.  in. 

'  0.491  Ib.  or  7.86  oz.  per  sq.  In. 
1.132  ft.  of  water  at  62°  F. 
13.58    in.  of  water  at  62°  F. 


•p      _  I  0.0005606  Ib.  per  sq.  in. 

I  0.015534    in.  of  water  at  62°  F. 


334 


TABLE   4. 


Properties  of  Saturated  Stei 


Absolute 
press're  Ibs. 
per  sq.  in. 

Tempera- 
ture 
deg.  F. 

Heat 
of  the 
liquid 

Heat  of  the 
vaporiza- 
tion 

Total 
heat 
above  82° 

1 

101.84 

69.8 

1034.7 

1104.5 

2 

126.15 

94.2 

1021.9 

1116.1 

3 

141.52 

109.6 

1012.2 

1121.8 

4 

153.00 

121.0 

1005.5 

1126.5 

5 

162.26 

130.3 

1000.0 

1130.3 

6 

170.07 

138.1 

995.5 

1133.6 

7 

176.84 

144.9 

991.4 

1136.3 

8 

182.86 

150.9 

987.8 

1138.7 

9 

188.27 

156.4 

984.5 

1140.9 

10 

193.21 

161.3 

981.4 

1142.7 

11 

197.74 

165.9 

978.6 

1144.5 

12 

201.95 

170.1 

976.0 

1146.1 

13 

205.87 

174.1 

973.6  . 

1147.7 

14 

209.55 

177.8 

971.2 

1149.0 

14.7 

212.00 

180.3 

969.7 

1150.0 

15 

213.03 

181.3 

969.1 

1150.4 

16 

216.31 

184.6 

967.0 

1151.6 

17 

219.43 

187.8 

965.0 

1152.8 

18 

222.40 

190.8 

963.1 

1153.9 

19 

225.24 

193.7 

961.2 

1154.9 

20 

227.95 

196.4 

959.4 

1155.8 

21 

230.56 

199.1 

957.7 

1156.8 

22 

233.07 

201.6 

956.0 

1157.6 

23 

235.50 

204.1 

954.4 

1158.5 

24 

237.82 

206.4 

952.9 

1159.3 

25 

240.07 

208.7 

951.4 

1160.1 

26 

242.26 

210.9 

949.9 

1160.8 

27 

244.36 

213.0 

948.5 

1161.5 

28 

246.41 

215.1 

947.1 

1162.2 

29 

248.41 

217.2 

945.8 

1163.0 

30 

250.34 

219.1 

944.4 

1163.5 

31 

252.22 

221.0 

943.1 

1164.1 

32 

254.05 

222.9 

941.8 

1164.7 

33 

255.84 

224.7 

940.6 

1165.3 

34 

257.59 

226.5 

939.4 

1165.9 

35 

259.29 

228.2 

938.2 

1166.4 

36 

260.96 

229.9 

937.1 

1167.0 

37 

262.58 

231.6 

935.9 

1167.5 

38 

264.17 

233.2 

934.8 

H68.0 

39 

265.73 

234.8 

933.7 

1168.5 

40 

267.26 

236.4 

932.6 

1169.0 

41 

268.76 

237.9 

931.6 

1169.5 

42 

270.23 

239.4 

930.6 

1170.0 

43 

271.66 

240.8 

929.5 

1170.3 

44 

273.07 

242.3 

928.5 

1170.8 

"Condensed  from  Peabody's  Steam  Tables.    1911  Edition. 
335 


Absolute 
press're  Ibs. 
per  sq.  in. 

Tempera- 
ture 
deg.  F. 

Heat 
of  the 
liquid 

Heat  of  the 
vaporiza- 
tion 

Total 
heat 
above  32° 

45 

274.46 

243.7 

927.5 

1171.2 

46 

275.82 

245.1 

926.6 

1171.7 

47 

277.16 

246.4 

925.6 

1172.0 

48 

278.47 

247.8 

924.7 

1172.5 

49 

279.76 

249.1 

923.8 

1172.9 

50 

281.03' 

250.4 

922.8 

1173.2 

51 

282.28 

251.7 

921.9 

1173.6 

52 

283.52 

253.0 

921.0 

1174.0 

53 

284.74 

254.2 

920.1 

1174.3 

54 

285.93 

255.4 

919.3 

1174.7 

55 

287.09 

256.6 

918.4 

1175.0 

56 

288.25 

257.8 

917.6 

1175.4 

57 

289.40 

259.0 

916.7 

1175.7 

58 

290.53 

260.1 

915.9 

1176.0 

59 

291.64 

261.3 

915.1 

1176.4 

60 

292.74 

262.4 

914.3 

1176.7 

61 

293.82 

263.5 

913.5 

1177.  C 

62 

294.88 

264.6 

912.7 

1177.3 

63 

295.93 

265.7 

911.9 

1177.6 

64 

296.97 

266.7 

911.1 

1177.8 

65 

298.00 

267.8 

910.4 

1178.2 

66 

299.02 

268.8 

909.6 

1178.4 

67 

300.02 

269.8 

908.9 

1178.7 

68 

301.01 

270.9 

908.1 

1179.0 

69 

301.99 

271.9 

907.4 

1179.3 

70 

302.96 

272.9 

906.6 

1179.5 

71 

303.91 

273.8 

905.9 

1179.7 

72 

304.86 

274.8 

905.2 

1180.0 

73 

305.79 

275.8 

904.5 

1180.3 

74 

306.72 

276.7 

903.8 

1180.5 

75 

307.64 

277.7 

903.1 

1180.8 

76 

308.54 

278.6 

902.4 

1181.0 

77 

309.44 

279.5 

901.8 

1181.3 

78 

310.33 

280.4 

901.1 

1181.5 

79 

311.21 

281.3 

900.4 

1181.7 

80 

312.08 

282.2 

899.8 

1182.0 

81 

312.94 

283.1 

899.1 

1182.2 

82 

313.79 

283.9 

898.5 

1182.4 

83 

314.63 

284.8 

897.8 

1182  6 

84 

315.47 

285.7 

897.2 

1182.9 

85 

316.30 

286.5 

896.6 

1183.1 

86    . 

317.12 

287.4 

895.9 

1183.3 

87 

.    317.93 

288.2 

895.3 

1183.5 

88 

318.73 

289.0 

894.7 

1183.7 

89 

319.53 

289.9 

894.1 

1184.0 

90 

320.32 

290.7 

893.5 

1184.2 

91 

321.10 

291.5 

892.9 

1184.4 

92 

321.88 

292.3 

892.3 

1184.6 

93 

322.65 

293.1 

891.7 

1184.8 

94 

323.41 

293.9 

891.1 

1185.0 

336 


Absolute 
press're  Ibs. 
per  sq.   in. 

Tempera- 
ture 
deg.  F. 

Heat 
of  the 
liquid 

Heat  of  the 
vaporiza- 
tion 

Total 
heat 
Above  32° 

95 

324.16 

294.6 

890.5 

1185.1 

96 

324.91 

295.4 

889.9 

1185.3 

97 

325.66 

296.2 

889.3 

1185.5 

98 

326.40 

296.9 

888.7 

1185.6 

99 

327.13 

297.7 

888.2 

1185.9 

100 

327.86 

298.5 

887.6 

1186.1 

101 

328.58 

299.2 

887.0 

1186.2 

102 

329.30 

299.9 

886.5 

1186.4 

103 

330.01 

300.6 

885.9 

1186.5 

104 

330.72 

301.4 

885.3 

1186.7 

105 

331.42 

302.1 

884.8 

1186.9 

106 

332.11 

302.8 

884.3 

1187.1 

107 

332.79 

303.5 

883.7 

1187.2 

108 

333.48 

304.2 

883.2 

1187.4 

109 

334  J6 

304.9 

882.6 

1187.6 

110 

334.83 

305.6 

882.1 

1187.7 

111 

335.50 

306.3 

881.6 

1187.9 

112 

336.17 

307.0 

881.0 

1188.0 

113 

336.83 

307.7 

880.5 

1188.2 

114 

337.48 

308.3 

880.0 

1188.3 

115 

338.14 

309.0 

879.5 

1188.5 

116 

338.78 

309.7 

879.0 

1188.7 

117 

339.42 

310.3 

878.5 

1188.8 

118 

340.06 

311.0 

878.0 

1189.0 

119 

340.69 

311.7 

877.4 

1189.1 

120 

341.31 

312.3 

876.9 

1189.2 

121 

341.94 

312.9 

876.4 

1189.3 

122 

342.56 

313.6 

875.9 

1189.5 

123 

343.18 

314.2 

875.4 

1189.6 

124 

343.79 

314.8 

875.0 

1189.8 

125 

344.39 

315.5 

874.5 

1190.0 

126 

345.00 

316.1 

874.0 

1190.1 

127 

345.60 

316.7 

873.5 

1190.2 

128 

346.20 

317.3 

873.0 

1190.  3 

129 

346.79 

317.9 

872.6 

1190.5 

130 

347.38 

318.6 

872.1 

1190.7 

131 

347.96 

319.2 

871.6 

1190.8 

132 

348.55 

319.8 

871.1 

1190.9 

133 

349.13 

320.4 

870.7 

1191.1 

134 

349.70 

320.9 

..     870.2 

1191.1 

135 

350.27 

321.5 

869.8 

1191.3 

136 

350.84 

322.1 

869.3 

1191.4 

137 

351.41 

322.7 

868.8 

1191.5 

138 

351.98 

323.3 

868.3 

1191.6 

139 

352.54 

323.9 

867.9 

1191.8 

140 

353.09 

324.4 

867.4 

1191.8 

141 

353.65 

325.0 

867.0 

1192.0 

142 

354.20 

325.6 

866.5 

1192.1 

143 

354.75 

326.2 

866.1 

1192.3 

144 

355.29 

326.7 

865.6 

1192.3 

337 


TABLE   5. 


Naperian  Logarithms. 

2.7182818  Log-    e    =    0.4342945 


=  M. 


1.0 

0.0000 

4.1 

1.4110 

7.2 

1.9741 

1.1 

0.0953 

4.2 

1.4351 

7.3 

1.9879 

1.2 

0.1823 

4.3 

1.4586 

7.4 

2.0015 

1.3 

0.2624 

4.4 

1.4816 

7.5 

2.0149 

1.4 

0.3365 

4.5 

1.5041 

7.6 

2.0281 

1.5 

0.4055 

4.6 

1.5261 

7.7 

2.0412 

1.6 

0.4700 

4.7 

1.5476 

7.8 

2.0541 

1.7 

0.5306 

4.8 

1.5686 

7.9 

2.0669 

1.8 

0.5878 

4.9 

1.5S92 

8.0 

2.0794 

1.9 

0.6419 

6.0 

1.6094 

8.1 

2.0919 

2.0 

0.6931 

6.1 

1.6292 

8.2 

2.1041 

2.1 

0.7419 

5.2 

1.6487 

8.3 

2.1163 

2.2 

0.7885 

6.3 

1.6677 

8.4 

2.1282 

2.3 

0.8329 

6.4 

1.6864 

8.5 

2.1401 

2.4 

0.8755 

6.5 

1.7047 

8.6 

2.1518 

2.5 

0.9163 

6.6 

1.7228 

8.7 

2.1633 

2.6 

0.9555 

6.7 

1.7405 

8.8 

2.1748 

2.7 

0.9933 

6.8 

1.7579 

8.9 

2.1861 

2.8 

1.0296 

5.9 

1.7750 

9.0 

2.1972 

2.9 

1.0647 

6.0 

1.7918 

9.1 

2.2083 

3.0 

.0986 

6.1 

1.8083 

9.2 

2.2192 

3.1 

.1312 

6.2 

1.8245 

9.3 

2.2300 

3.2 

.1632 

6.3 

1.8405 

9.4 

2.2407 

8.3 

.1939 

6.4 

1.8563 

9.5 

2.2513 

8.4 

.2238 

6.5 

1  .8718 

9.6 

2.2618 

3.5 

.2528 

6.6 

1.8871 

9.7 

2.2721 

3.6 

.2809 

6.7 

1.9021 

9.8 

2.2824 

3.7 

.3083 

6.8 

1.9169 

9.9 

2.2925 

3.8 

.3350 

6.9 

1.9315 

10.0 

2.3026 

3.9 

1.3610 

7.0 

1.9459 

4.0 

1.3863 

7.1 

1.9601 

TABLE   6. 
"Water  Conversion  Factors.* 


U.  S.  gallons 
U.  S.  gallons 
U.  S.  gallons 
U.  S.  gallons 


Cubic  inches  of  water  (39.1°)  X 
Cubic  inches  of  water  (39.1°)  X 
Cubic  inches  of  water  (39.1°)  X 
Cubic  feet  of  water  (39.1°)  X 
Cubic  feet  of  water  (39.1°)  X 
Cubic  feet  of  water  (39.1°)  X 
Pounds  of  water  X 

Pounds  of  water 
Pounds  of  water  X 


231.00000 
3.78 

0.036024 
0.004329 
0.576384 
62.425 
7.48 
0.028 
27.72 
0.01602 
0.12 


pounds. 
=  cubic  feet, 
cubic  inches. 

liters. 

pounds. 

U.  S.  gallons. 

ounces. 

pounds. 

U.  S.  gallons. 

tons. 

cubic  inches. 

cubic  feet. 

U.  S.  gallons. 


•American  Machinist  Hand  Book. 
338 


TABLE   7. 
Volume  and  Weight  of  Dry  Air  at  Different  Temperatures. * 

Under   a   constant   atmospheric  pressure   of   29.92    inches   of 
mercury,   the  volume  at  32°   F.   being   1. 


Temp, 
deg.  F. 

Volume 

Weight 
per  cu.  ft. 

Temp, 
deg.  P. 

Volume 

Weight 
per  cu.  ft. 

0 

.935 

.0864 

500 

1.954 

.0413 

12 

.960 

.0842 

552 

2.056 

.0385 

22 

.980 

.0824 

600 

2.150 

.0376 

32 

.000 

.0807 

650 

2.230 

.0357 

42 

.020 

.0791 

700 

2.362 

.0338 

52 

.041 

.0776 

750 

2.465 

.0328 

62 

.061 

.0761 

800 

2.566 

.0315 

72 

.082 

.0747 

850 

2.668 

.0303 

82 

.102 

.0733 

900 

2.770 

.0292 

92 

1.122 

.0720 

950 

2.871 

.0281 

102 

1.143 

.0707 

1000 

2.974 

.0268 

112 

1.163 

.0694 

1100 

3.177 

.0254 

122 

1.184 

.0682 

1200 

3.381 

.0239 

132 

1.204 

.0671 

1300 

3.584 

.0225 

142 

1.224 

.0659 

1400 

3.788 

.0213 

152 

1.245 

.0649 

1500 

8.993 

.0202 

162 

1.265 

.0638 

1600 

4.196 

.0192 

172 

1.285 

.0628 

1700 

4.402 

.0183 

182 

1.306 

.0618 

1800 

4.605 

.0175 

192 

1.326 

.0609 

1900 

4.808 

.0168 

202 

1.347 

.0600 

2000 

5.012 

.0161 

212 

1.367 

.0591 

2100 

5.217 

.0155 

230 

1.404 

.0575 

2200 

5.420 

.0149 

250 

1.444 

.0559  • 

2300 

5.625 

.0142 

275 

1.495 

.0540 

2400 

5.827 

.0138 

300 

1.546 

.0522 

2500 

6.032 

.0133 

325 

1.597 

.0506 

2600 

6.236 

.0130 

350 

1.648 

.0490 

2700 

6.440 

.0125 

875 

1.689 

.0477 

2800 

6.644 

.0121 

400 

1.750 

.0461 

2900 

6.847 

.0118 

450 

1.852 

.0436 

•    3000 

7.051 

.0114 

*Suplee's  M.  E.  Reference  Book. 


239 


TABLE   8. 

Weight   of  Pure   Water  per    Cubic   Foot   at  Various 
Temperatures.* 


Temp, 
deg. 
F. 

Weight 
Ibs.  per 
cu.   ft. 

B.   t.   U. 
per  pound 
above  32 

Temp, 
deg. 
F. 

Weight 
Ibs.  per 
cu.   ft. 

B.   t.   u. 
per  pound 
above  32 

32 

62.42 

0.00 

77 

62.26 

45.04 

33 

62.42 

1.01 

78 

62.25 

46.04 

34 

62.42 

2.02 

79 

62.24 

47.04 

35 

62.42 

3.02 

80 

62.23 

48.03 

36 

62.42 

4.03 

81 

62.22 

49.03 

37 

62.42 

5.04 

82 

62.21 

50.03 

38 

62.42 

6.04 

83 

62.20 

51.02 

39 

62.42 

7.05 

84 

62.19 

52.02 

40 

62.42 

8.05 

85 

62.18 

53.02 

41 

62.42 

9.05 

86 

62.17 

54.01 

42 

62.42 

10.06 

87 

62.16 

55.01 

43 

62.42 

11.06 

88 

62.15 

56.01 

44 

62.42 

12.06 

89 

62.14 

57.00 

45 

62.42 

13.07 

90 

62.13 

58.00 

46 

62.42 

14.07 

91 

62.12 

59.00 

47 

62.42 

15.07 

92 

62.11 

60.00 

48 

62.41 

16.07 

93 

62.10 

60.99 

49 

62.41 

17.08 

94 

62.09 

61.99 

50 

62.41 

18.08 

95 

62.08 

62.99 

51 

62.41 

19.08 

96 

'62.07 

63.98 

52 

62.40 

20.08 

97 

62.06 

64.98 

53 

62.40 

21.08 

98 

62.05 

65.98 

54 

62.40 

22.08 

99 

62.03 

66.97 

55 

62.39 

23.08 

100 

62.02 

67.97 

56 

62.39 

24.08 

101 

62.01 

68.97 

'  57 

62.39 

25.08 

102 

62.00 

69.96 

58 

62.38 

26.08 

103 

61.99 

70.96 

59 

62.38 

27.08 

104 

61.97 

71.96 

60 

62.37 

28.08 

105 

61.96 

72.95 

61 

62.37 

29.08 

106 

61.95 

73.95 

62 

62.36 

30.08 

107 

61.93 

74.95 

63 

62.36 

31.07 

108 

61.92 

75.95 

64 

62.35 

32.07 

109 

61.91 

76.94 

65 

62.34 

33.07 

110 

61.89 

77.94 

66 

62.34 

34.07 

111 

61.88 

78.94 

67 

62.33 

35.07 

112 

61.86 

79.93 

68 

62.33 

36.07 

113 

61.85 

80.93 

69 

62.32 

37.06 

114 

61.83 

81.93 

70 

62.31 

38.06 

115 

61.82 

82.92 

71 

62.31 

39.06 

116 

61.80 

83.92 

72 

62.30 

40.05 

117 

61.78 

84.92 

73 

62.29 

41.05 

118 

61.77 

85.92 

74 

62.28 

42.05 

119 

61.75 

86.91 

75 

62.28 

43.05 

120 

61.74 

87.91 

76 

62.27 

44.04 

121 

61.72 

88.91 

'Kent's  M.  E.  Pocket-Book.    8th  Edition. 


340 


Temp, 
deg. 
F. 

Weight 
Ibs.  per 
cu.  ft. 

B.   t.    u. 
per  pound 
above  32 

Temp, 
deg. 

Weight 
Ibs.  per 
cu.  ft. 

B.   t.    u. 
per  pound 
above  32 

122 

61.70 

89.91 

167 

60.83 

134.86 

123 

61.68 

90.90 

168 

60.81 

135.86 

124 

61.67 

91.90 

169 

60.79 

136.86 

125 

61.65 

92.90 

170 

60.77 

137.87 

126 

61.63 

93.90 

171 

60.75 

138.87 

127 

61.61 

94.89 

172 

60.73 

139.87 

128 

61.60 

95.89 

173 

60.70 

140.87 

129 

61.58 

96.89 

174 

60.68 

141.87 

130 

61.56 

97.89 

175 

60.66 

142.87 

131 

61.54 

98.89 

176 

60.64 

143.87 

132 

61.52 

99.88 

177 

60.62 

144.88 

133 

61.51 

100.88 

178 

60.59 

145.88 

134 

61.49 

101.88 

179 

60.57 

146.88 

135 

61.47 

102.88 

180 

60.55 

147.88 

136 

61.45 

103.88 

181 

60.53 

148.88 

137 

61.43 

104.87 

182 

60.50 

149.89 

138 

61.41 

105.87 

183 

60.48 

150.89 

139 

61.39 

106.87 

184 

60.46 

151.89 

140 

61.37 

107.87 

185 

60.44 

152.89 

141 

61.36 

108.87 

186 

60.41 

153.89 

142 

61.34 

109.87 

187 

60.39 

154.90 

143 

61.32 

110.87 

188 

60.37 

155.90 

144 

61.30 

111.87 

189 

60.34 

156.90 

145 

61.28 

112.86 

190 

60.32 

157.91 

146 

61.26 

113.86 

191 

60.29 

158.91 

147 

61.24 

114.86 

192 

60.27 

159.91 

148 

61.22 

115.86 

193 

60.25 

160.91 

149 

61.20 

116.86 

194 

60.22 

161.92 

150 

61.18 

117.86 

195 

60.20 

162.92 

151 

61.16 

118.86 

196 

60.17 

163.92 

152 

61.14 

119.86 

197 

60.15 

164.93 

153 

61.12 

120.86 

198 

60.12 

165.93 

154 

61.10 

121.86 

199 

60.10 

166.94 

155 

61.08 

122.86 

200 

60.07 

167.94 

156 

61.06 

123.86 

201 

60.05 

168.94 

157 

61.04 

124.86 

202 

60.02 

169.95 

158 

61.02 

125.86 

203 

00.00 

170.95 

159 

61.00 

126.86 

204 

59.97 

171.96 

160 

60.98 

127.86 

203 

59.95 

172.96 

161 

60.96 

128.86 

206 

59.92 

173.97 

162 

60.94 

129.86 

207 

59.89 

174.97 

163 

60.92 

130.86 

208 

5y.87 

175.98 

164 

60.90 

131.86 

209 

59.84 

176198 

165 

60.87 

132.86 

210 

59.82 

177.99 

166 

60.85 

133.86 

211 

59.79 

178.99 

212 

59.76 

180. 

TABLE   9. 
Boiling:  Point  of  Water  at  Different  Heights  of  Vacuum. 


Temp. 
F. 

Height  of 
mercury  in 
vacuum  tube 
in  inches 

Temp. 
F. 

Height  of 
mercury  in 
vacuum  tube 
in  inches 

212.0 

0.00 

175.8 

16.00 

210.3 

1.00 

172.6 

17.00 

208.5 

2.00 

169.0 

18.00 

206.8 

3.00 

165.3 

19.00 

204.8 

4.00 

161.2 

20.00 

202.9 

5.00 

156.7 

21.00 

200.9 

6.00 

151.9 

22.00 

199.0 

7.00 

146.5 

23.00 

196.7 

8.00 

140.3 

24.00 

194.5 

9.00 

133.3 

25.00 

192.2 

10.00 

124.9 

26.00 

189.7 

11.00 

114.4 

27.00 

187.3 

12.00 

108.4 

28.00 

184.6 

13.00 

102.0 

29.00 

181.3 

14.00 

98.0 

29.92 

178.9 

15.00 

TABLE  10. 

Weight  of  Water  with  Air  per  Cubic  Foot  at  Different 
Temperatures   anil   at    Saturation. 


ft 

il 
is 

!>  60 

ft 

I 

II 

'Z  08 

£a 

ft 

s 

Is 

12 

>  60 

ft 

a 

I 

£  2 
w-S 
£2 

£  60 

ft 

I 

is 

12 

t>  60 

ft 

ft 

£ 

ii 

a>  oS 
>  ** 
!>  60 

-20 

0.166 

2 

0.529 

24 

1.483 

46 

3.539 

68 

7.480 

90 

14.790 

—19 

0.174 

3 

0.554 

25 

1.551 

47 

3.667 

69 

7.726 

91 

15.234 

—18 

0.184 

4 

0.582 

26 

1.623 

48 

3.800 

70 

7.980 

92 

15.689 

—17 

0.196 

5 

0.610 

27 

1.697 

49 

3.936 

71 

8.240 

93 

16.155 

—16 

0.207 

6 

0.639 

28 

1.773 

50 

4.076 

72 

8.508 

94 

16.634 

—15 

0.218 

7 

0.671 

29 

1.853 

51 

4.222 

73 

8.782 

95 

17.124 

—14 

0.231 

8 

0.704 

30 

1.935 

52 

4.372 

74 

9.066 

96 

17.626 

—13 

0.243 

9 

0.739 

31 

2.022 

53 

4.526 

75 

9.356 

97 

18.142 

—12 

0.257 

10 

0.776 

32 

2.113 

54 

4.685 

76 

9.655 

98 

18.671 

—11 

0.270 

11 

0.816 

33 

2.194 

55 

4.849 

77 

9.962 

99 

19.212 

—10 

0.285 

12 

0.856 

34 

2.279 

56 

5.016 

78 

10.277 

100 

19.766 

—  9 

0.300 

13 

0.898 

35 

2.366 

57 

5.191 

79 

10.601 

101 

20.335 

—  8 

0.316 

14 

0.941 

36 

2.457 

58 

5.370 

80 

10.934 

102 

21.017 

7 

0.332 

15 

0.986 

37 

2.550 

59 

5.555 

81 

11.27.") 

103 

21.514 

—  6 

0.350 

16 

1.032 

38 

2.646 

60 

5.745 

82 

11.626 

104 

22.125 

—  5 

0.370 

17 

1.080 

39 

2.746 

61 

5.941 

83 

11.987 

105 

22.750 

«—  4 

0.389 

18 

1.128 

40 

2.849 

62 

6.142 

84 

12.356 

106 

23.392 

—  3 

0.411 

19 

1.181 

41 

2.955 

63 

6.349 

85 

12.736 

107 

24.048 

—  2 

0.434 

20 

1.235 

42 

3.064 

64 

6.563 

86 

13.127 

108 

24.720 

—  1 

0.457 

21 

1.294 

43 

3.177 

65 

6.782 

87 

13.526 

109 

25.408 

0 

0.481 

22 

1.355 

44 

3.294 

66 

7.009 

88 

13.937 

110 

26.112 

1 

0.505 

23 

1.418 

45 

3.414 

67 

7.241 

89 

14.359 

342 


••    « 

£     £ 


I  S3 


53 


i-li-l(M(M<N<MCOCOCOCOC?      I    CO 


SSSSSS  ISS 


,-H  eg      co 


COt^-I^-t^-OOOOOOOOWOOOOwGOOOOOOSOiCiCiOiOSOi 


° I i!i!!!i§§!i!ll§§i§§§i§!  I 


343 


TABLE  12. 

Properties   of  Air  with   Moisture  under  Pressure  of  One 
Atmosphere.  * 


fto 

a 

ft 

Mixtures  of  air  saturated 

3)  0) 

q  s-i 

•o 

m 

go 

£0 

£« 

Ij 

with  vapor. 

S  a> 

• 

&  be 

J*~ 

£  3 
~*  Oj 

*Sh 

Weight  of  cubic 

5 

2ft 

P 

*s 

fc  C 

o.2 

c  to 

•—  & 

L  •**  C 

%foot  of  the 

2 

«H 

. 

ja 

£'£ 

+»»" 

P,   4> 

~  CS  K 

^mixture. 

0 

p 

0"^ 

'33 

s 

'U  »Q 

ft 

i>^-' 

<D  O  O 

<D 

. 

"^ 

'3 

^*  t-l     • 

4^ 

1 

2- 

gf 

°£? 

~2g 

•^  03 

03 

•e 

rt 

«_ 

flj 

>j  . 

P^c 

«s 

2 

.see 

&  3 

gj5a 

C  ^ 

l| 

a—  • 

03 

"ri 

*w  O 
ft 

o££ 

M 

1 

»H' 

O  CJ 

-P  a; 

«2  ^ 

oS0 

0  0 

ft 

*°  fl 

O 

1-1  OJ 

c  > 

w 

Ig 

ft 

1| 

11 

o 
So 

.S.S3  *-. 
ao*-1  C 

§S 

"So 

sl 

O 

°a> 

~cs 

bo 

1 

II 

o> 

j>4J 

03          ft 

&% 

il 

II 

M 

If 

Us 

|i 

i 

2 

3 

4 

5 

c 

7 

8 

9 

10 

11 

12 

0 

.935 

.0864 

0.044 

29.877 

.0863 

.000079 

.086379 

.00092 

1092.40 

48.5 

12 

.960 

.0842 

0.074 

29.849 

.0840 

.000130 

.084130 

.00115 

646.10 

50.1 

22 

.980 

.0824 

0.118 

29.803 

.0821 

.000202 

.082302 

.00245 

406.40 

51.1 

32 

1.000 

.0807 

0.181 

29.740 

.0802 

.000304 

.080504 

.00379 

263.81 

3289"  6 

52.0 

42 

1.020 

.0791 

.0267 

29.654 

.0784 

.000440 

.078840 

.00561 

178.18 

2252.0 

53.2 

52 

1.041 

.0766 

0.388 

29.533 

.0766 

.000627 

.077227 

.00819 

122.17 

1595.0 

54.0 

60 

1.057 

.0764 

0.522 

29.399 

.0751 

.000830 

.075252 

.01251 

92.27 

1227.0 

55.0 

62 

1.061 

.0761 

0.556 

29.365 

.0747 

.000881 

.075581 

.01179 

84.79 

1135.0 

55.2 

70 

1.078 

.0750 

0.754 

29.182 

.0731 

.001153 

.073509 

.01780 

64.59 

882.0 

56.2 

72 

1.082 

.0747 

0.785 

29.136 

.0727 

.001221 

.073921 

.01680 

59.54 

819.0 

56.3 

82 

1.102 

.0733 

1.092 

28.829 

.0706 

.001667 

.072267 

.02361 

42.35 

600.0 

57.2 

92 

1.122 

.0720 

1.501 

28.420 

.0684 

.002250 

.070717 

.03289 

30.40 

444.0 

58.4 

100 

1.139 

.0710 

1.929 

27.992 

.0664 

.002848 

.069261 

.04495 

23.66 

356.0 

59.1 

102 

1.143 

.0707 

2.036 

27.885 

.0659 

.002997 

.068897 

.04547 

21.98 

334.0 

59.5 

112 

1.163 

.0694 

2.731 

27.190 

.0631 

.003946 

.067042 

.06253 

15.99 

253.0 

60.6 

122 

1.184 

.0682 

3.621 

26.300 

.0599 

.005142 

.065046 

.08584 

11.65 

194.0 

61.7 

132 

1.204 

.0671 

4.752 

25.169 

.0564 

.006639 

.063039 

.11771 

8.49 

151.0 

62.5 

142 

1.224 

.0660 

6,165 

23.756 

.0524 

.008473 

.060873 

.16170 

6.18 

118.0 

63.7 

152 

1.245 

.0649 

7.930 

21.991 

.0477 

.010716 

.058416 

.22465 

4.45 

93.3 

64.7 

162 

1.265 

.0638 

10.099 

19.822 

.0423 

.013415 

.055715 

.31713 

3.15 

74.5 

65.8 

172 

1.285 

.0628 

12.758 

17.163 

.0360 

.016682 

.052682 

.46338 

2.16 

59.2 

66.9 

182 

1.306 

.0618 

15.960 

13.961 

.0288 

.020536 

.049336 

.71300 

1.402 

48.6 

68.0 

192 

1.326 

.0609 

19.828 

10.093 

.0205 

.025142 

.045642 

1.22643 

.815 

39.8 

69.0 

202 

1.347 

.0600 

24.450 

5.471 

.0109 

.030545 

.041445 

2.80230 

.357 

32.7 

70.0 

In- 

212 

1.367 

.0591 

29.921 

0.000 

.0000 

.036820 

.036820 

finite 

.000 

27.1 

71.1 

'Carpenter's  H.  &  V.  B.  and  Sturtevant's  Mech.  Draft. 


344 


TABLE   13. 
De\v-Folnts  of  Air  According  to  Its  Hygrometric  State.* 


Relative  moisture 

Temp* 

90% 

80% 

70% 

60% 

50% 

c. 

F. 

C. 

F. 

C. 

F. 

0. 

F. 

C. 

F. 

C. 

F. 

0 

32.0 

—  1.5 

29.3 

—  3.0 

26.6 

—  4.9 

23.2 

—  6.5 

20.3 

—  9.2 

15.4 

2 

35.6 

0.9 

33.6 

—  0.9 

30.4 

—  2.5 

27.5 

—  4.8 

23.4 

—  7.1 

19.2 

4 

39.2 

2.4 

36:3 

0.9 

33.6 

—  0.9 

30.4 

—  2.9 

26.8 

—  5.3 

22.5 

6 

42.8 

4.5 

40.1 

2.9 

37.2 

0.9 

33.6 

—  1.3 

29.7 

—  3.7 

25.3 

8 

46.4 

6.4 

43.5 

4.5 

40.1 

2.7 

36.9 

0.6 

33.1 

—  1.9 

28.6 

10 

50.0 

8.5 

47.3 

6.8 

44.2 

4.5 

40.1 

2.5 

36.5 

0.0 

32.0 

12 

53.6 

10.5 

50.9 

8.5 

47.3 

6.8 

44.2 

4.3 

39.7 

2.0 

35.6 

14 

57.2 

12.3 

54.1 

10.5 

50.9 

8.5 

47.3 

6.2 

43.2 

3.7 

38.7 

16 

60.8 

14.4 

57.9 

12.6 

54.7 

10.5 

50.9 

8.3 

46.9 

5.6 

42.1 

18 

64.4 

16.5 

61.7 

14.6 

58.3 

12.4 

54.3 

10.0 

50.0 

7.4 

45.3 

20 

68.0 

18.3 

64.9 

16.5 

61.7 

14.4 

57.9 

11.9 

53.4 

9.2 

48.6 

22 

71.6 

20.3 

68.5 

18.4 

65.1 

16.3 

61.3 

13.7 

56.7 

11.6 

52.8 

24 

75.2 

22.2 

72.1 

20.5 

68.9 

18.4 

65.1 

15.6 

60.0 

13.0 

55.4 

26 

78.8 

24.4 

75.9 

22  2 

72.1 

20.1 

68.2 

17.6 

63.6 

14.7 

58.5 

28 

82.4 

26.3 

79.3 

2i'.2 

75.6 

22.0 

71.6 

19.5 

67.1 

17.5 

63.5 

30 

86.0 

28.3 

82.9 

26.3 

79.3 

23.9 

75.0 

21.5 

70.7 

18.3 

64.9 

'Bulletin  21,  Int.  Ass'n  of  Refrig. 

Psychrometric  Charts  Recent  Tests. 

In  recent  years  a  highly  technical  study  o-f  humidity 
and  its  control  has  been  made  by  Mr.  Willis  H.  Carrier.  Fig. 
A  shows,  merely  for  the  sake  of  comparison,  how  closely  his 

results  checked  the  earlier 
values  obtained  by  the  Gov- 
ernment Weather  Bureau.  The 
following  charts,  Figs.  B  and 
C,  summarize  the  results  of 
Mr.  Carrier's  experiments. 
Fig.  C  is  a  part  of  Fig.  B 
drawn  to  a  larger  scale. 


< 

30* 
20   fe 


70      ORV*BULB80 

Fig.   A. 

As  one  illustration  of  the  use  of  the  chart,  refer  to  Fig 
C  with  air  at  40  degrees  and  40  per  cent,  humidity.  If  this 
air  be  heated  to  100  degrees  without  addition  of  moisture 
it  will  be  seen  by  interpolation  that  the  humidity  drops 
to  about  8  per  cent.  If  the  same  be  heated  to  100  degrees 
and  enough  moisture  be  added  to  keep  the  relative  humid- 
ity at  40  per  cent.,  then  the  absolute  humidity  changes  from 
15  grains  to  120  grains  per  pound  of  air.  These  figures 
may  be  reduced  to  grains  per  cubic  foot  by  dividing  by  the 
volume  per  pound  as  given  in  the  second  column  and  will 
be  found  to  check  closely  with  those  given  by  Fig.  7  and 
Table  9.  Almost  any  other  points  relating  to  changes  in 
volume,  humidity  and  contained  heat  may  be  easily  worked 
out  by  these  curves.  045 


346 


347 


TABLE  14. 
Fuel  Value  of  American  Coals.* 


Coal 
Name  or  locality 

Fuel  value  per  pound 
of  coal. 

B.  t.  u. 
calculated. 

13.  t.  u.  by 
calorimeter. 

13* 

iai* 

£g    & 

Or;  fl'O 

Hi 

ARKANSAS. 
Spadra,    Johnson    Co. 

14,420 

9,215 

13,500 
8,500 

14,020 
13,097 

14,391 
15,198 
9,326 

13,714 
13,414 

14,199 
12,300 

12,962 
14,200 

11,812 
11,756 

11,781 
9,035 
9.739 
13,123 

8,703 

9,890 
11,756 

13,104 
12,936 

9,450 
14,273 

14.90 
12.22 
12.17 
9.54 

14.04 
8.80 

12.19 
9.35 
10.09 
13.58 

14.50 
13.56 

9.01 

14.89 
16.76 
9.65 

10.24 
12.17 

14.20 
13.90 

14.70 
12.73 
13.46 
13.39 

9.78 
13.41 

14.71 

14.70 

Coal  Hill,  Johnson  Co              • 

Huntingdon  Co 

Lignite    _  _ 

COLORADO. 
Lignite    _ 

Lignite,   slack 

ILLINOIS. 
Big1    Muddv,    Jackson    Co. 

Colchester,*   Slack                  __      

Giliespie,  Macoupin  Co.    _               _    _    _    _ 

Mercer  Co. 

INDIANA. 
Block    - 

Cannel 

IOWA. 
Good   cheer  .  

KENTUCKY. 
Caking1 

Cannel 

Lignite    _ 

MISSOURI. 
Bevier    Mines- 

NEW  MEXICO. 
Coal    — 

OHIO. 
Briar   Hill,    Mahoning    Co  

Hocking    Vallev 

PENNSYLVANIA. 
Anthracite 

Anthracite,   pea          _    

Pittsburgh   (average)      --  

Youghiogheney 

TEXAS. 
Fort  Worth 

Lignite 

WEST  VIRGINIA. 
Pocahontas 

New  River                    

*Sturtev ant's  "Mechanical  Draft." 


348 


TABLE   15. 
Capacities  of  Chimneys.11 


« 

s 

• 

s 

03   <O 

ill 

G  ^  *-—  ' 

Maximum  sq.   ft.   of  cast  iron  radiating 
surface  and  B.  t.  u.  for  a  flue  of  the 
given  diameter  and  height 

& 

a 

a 

»o 

(M 

a 
.£? 

2 

% 

,q 
to 

3 

d 

9 

i 

£ 

3 

^ 
£0 

s 

<M 

oo 

I 

43 
I 

6 
7 
8 
9 
10 
12 
15 
18 

Steam 

146 
243 
36500 

228 
379 
57000 

327 
544 

81750 

445 
742 
111250 

582 
145500 

909 

1514 
227250 

1537 
2561 
384250 

2327 

3878 
581750 

175 
291 
43750 

273 
455 
68250 

392 
653 

98000 

534 
890 
133500 

698 
1163 
174500 

1090 
1817 
272500 

1844 
3073 
461000 

2792 
4653 
698000 

204 
340 
51000 

319 
531 
79750 

457 
762 
114250 

623 
1038 
155750 

814 
1357 
203500 

1272 
2120 
318000 

2151 

3586 
537750 

3257 

5-129 
814250 

233 
388 
58250 

364 
607 
91000 

523 

871 
130750 

712 
1187 
178000 

930 
1551 
232500 

1454 
2423 
363500 

2458 
4098 
614500 

3722 
6204 
930500 

262 
437 
65500 

410 
683 
102500 

588 
980 
147000 

801 
1335 
200250 

1047 
1745 
261750 

1636 
2726 
409000 

2766 
4610 
691500 

4188 
6980 
1047000 

291 
485 
72750 

455 
758 
113750 

653 

1083 
163250 

890 
1483 
222500 

1163 

1938 
290750 

1817 

3028 
454250 

3073 
5122 
768250 

4653 
7755 
1163250 

iot  water 
B.  t.  u.  __. 

Steam 

Hot  water  _. 
B.  t.  u. 

Steam 

Hot  water 

B.  t.  u.  _  _ 

Steam 

Hot  water      

B.  t.  u.  -_- 

Steam 

Hot  water 

B.  t.  u. 

Steam 

Hot  water 

B.  t.  u. 

Steam 

Hot  water    __ 

B.  t.  u.  - 

Steam   

Hot  water  

B    t    u 

Radiation  is  calculated  at  250  B.  t.  u.  steam,  150  B.  t.  u.  water. 
*The  Model  Boiler  Manual. 


349 


TABLE  16. 
Equalization     of     Smoke    Flues — Commercial     Sizes.* 


Rectangular  Outside 

"ined  flue  iron 

outside  of  tile  stack 


7x7 

8y2xsy2  10 

sy2xi3  11 

8y2xis  12 

13x13  14 

13x18  17 
18x18 


Round  flue  tile  lining  is  listed  by  its  inside  measurement. 
Rectangular  lining  by  outside  measurement. 

TABLE  17. 
Dimensions   of  Registers.* 


Inside 
diameter 
lined  flue 

Brick  flue 
not  lined 
well  built 

] 

01 

6 

7 
8 
9 
10 
13 
15 
18 

8%x8% 

8y2x8y2 

8y2xsy2 

8V2xl3 
8^x13 
13x13 
33x17 
17x21^ 

Size  of 
opening, 
inches 

Nominal 
area  cf 
opening, 
square 
inches 

Effective 
area  of 
opening, 
square 
inches 

Tin  box  size, 
inches 

Extreme 
dimensions  of 
register  face, 
inches 

6x10 
8x10 

GO 
80 

40 
53 

6*g  x  10i9a 
8%  x  lOXs 

JSxilS 

8x12 

96 

64 

8^ 

!  X  12' 

/a 

9%  x  18% 

8x15 

120 

80 

8^8  x  16H 

9%  x  16Ji 

9x12 

108 

72 

91 

1x12 

1 

10%  x  13% 

9x14 

126 

84 

91J  x  141 

h 

10%  x  15% 

10x12 

120 

80 

10} 

!x  12 

k 

llji  x  18}8 

10x14 
10x16 
12x15 

140 
160 

180 

93 
107 
120 

10} 
101 

12^ 

Xl4 
ixl6 
xl5 

k 

lllg  X151J 
llig  x  17% 
14A  x  17 

12x19 

228 

152 

12fc 

!xl95 

I 

14^x21 

14x22 

808 

205 

14%  x  22? 

i 

16H  x  24^ 

15x25 

375 

250 

157/ 

X255 

3 

17/4  x  27/i 

16x20 

820 

213 

\w 

5x20? 

i 

jg  6  x  22i6» 

16x21 

384 

256 

1Q7/ 

x24? 

18  ,\  x  26  A 

20x20 

400 

267 

20} 

x20j 

22%  x  22% 

20x24 

480 

820 

20} 

i 

22%  x  26% 

20x26 

520 

847 

x26| 

22%  x  28% 

21x29 

609 

403 

21} 

23%  X  81% 

27x27 

729 

486 

27} 

x  27j 

29%  x  29% 

27x88 

1026 

684 

27} 

x38j 

29%  x  403/S 

80x80 

900 

600 

80}, 

x30} 

32%  x  32% 

Dimensions  of  different  makes  of  registers  vary  slightly.     The  above 
are  for  Tuttle  &  Bailey  manufacture. 

•The  Model  Boiler  Manual. 


350 


TABLE  18. 


Capacities  of  Warm  Air  Furnaces  of  Ordinary  Construction  in 
Cubic  Feet  of  Space  Heated.* 


Divided  space 

Fire-pot 

Undivided  space 

+10° 

0° 

—10° 

Diam. 

Area 

+  10° 

0° 

—10° 

12000 

10000 

8000 

18  in. 

1.8  sq.  ft. 

17000 

14000 

12000 

14000 

12000 

10000 

20 

2.2 

22000 

17000 

14000 

17000 

14000 

12000 

22 

2.6 

26000 

22000 

17000 

22000 

18000 

14000 

24 

8.1 

80000 

26000 

22000 

2(5000 

22000 

18000 

26 

3.7 

85000 

80000 

26000 

80000 

26000 

22000 

28 

4.8 

40000 

85000 

80000 

85000 

80000 

26000 

80 

4.9 

50000 

40000 

85000 

TABLE   19. 
Capacities    of    Hot-Air    Pipes    and    Registers.! 


g 

a  t-i 

«W*Ji-( 

fl 

a 

o 

o 

1 

gfe 

.2? 

«a  ^ 

1 

"1 

•*•>  t< 

^a* 

|| 

& 

s 

If*! 

s  ° 

«£  o  EJ 

•HO 

"3  ° 

"3 

• 

a 

o 

>  T1 

t*    &H 

CJ  >f 

O 

O 

§ 

GO 

III 

HI 

•^  C3  O  g 
O  w  53  -^ 

2  o 

51 

11 

6x8 

6  in. 

4x8 

400 

450 

500 

8x8 

7   " 

4x10 

450 

500 

560 

8x10 

8   " 

4x10 

500 

850 

880 

8x12 

8  " 

4x11 

800    ' 

1000 

1050 

9x12 

9   " 

4x12 

1050 

1250 

1320 

9x14 

9  " 

4x14 

1050 

1350 

1450 

10x12 

10   " 

4x14 

1500 

1650 

1800 

10x14 

10  " 

6x10 

1800 

2000 

2200 

10x16 

10   " 

6x10 

1800 

2000 

2200 

12x14 

12   " 

6x12 

2200 

2300 

2500 

12x15 

12   " 

6x12 

2250 

2300 

2500 

12x17 

12   " 

6x14 

2300 

2600 

2800 

12x19 

12    " 

6x14 

2300' 

2600 

2800 

14x18 

14   " 

6x16 

2800 

3000 

3200 

14x20 

14    " 

6x16 

2900 

3000 

3200 

14x22 

14    " 

8x16 

3000 

3200 

3400 

16x20 

16   " 

8x18 

3600 

4000 

4250 

16x24 

16  " 

8x18 

3700 

4000 

4250 

20x24 

18   " 

10x20 

4800 

5400 

5750 

20x26 

20  " 

10x24 

6000 

7000 

7450 

•Federal  Furnace  League  Handbook. 
tKidder's  Arch,  and  B'ld'rs.  Pocket-Book. 

351 


TABLE  20. 
Air  Heating   Capacity  of  Warm   Air  Furnaces.* 


Total 

cross  sec. 

Fire-pot 

Casing 

area  of 
heat 

No.  and  size  of  heat  pipes  that 
may  be  supplied 

pipes 

Diam 

Area 

Diam. 

18  in. 

1.8  sq.  ft. 

30"-32" 

180  sq.  in. 

3-9"  or  4-8* 

20  " 

2.2 

34"-36" 

280      " 

2-10"  and  2-9"  or  3-9"  and  2-8" 

22  " 

2.6 

36"-40" 

360      " 

3-10*  and  2-9*  or  4-9*  and  2-8" 

24  " 

3.1 

40"-44" 

470      " 

3-10",  1-9"  and  2-8"  or  2-10"  and  5-8* 

26   " 

3.7 

44"-50" 

565      " 

5-10"  and  3-9"  or  3-10",  4-9*  and  2-8" 

28   " 

4.3 

48"-56" 

650      " 

2-12*,  3-10"  and  3-9"  or  5-10",  3-9"  and  2-8* 

30  " 

4.9 

52"-60" 

730      " 

3-12",  3-10"  and  3-9"  or  5-10",  5-9"  and  1-8" 

TABLE  21. 

Sectional   Area    (Square   Inches)    of  Vertical    Hot    Air  Flues, 
Natural  Draft,  Indirect  System.t 

Outside  temperature  50°  F.    Flue  temperature  90°  F. 


STEAM 

WATER 

Sq.  ft. 
cast  iron 

a     ' 

a 

'•S 

£ 

radiation 

jjjj 

§M 
«j 

2  S 

£H  to 

en  f-i 

^    ^> 

§1 

•J.    CO 

11 

II 

0  to    50 

100 

75 

63 

60 

75 

63 

60 

60 

50          75 

150 

113 

94 

80 

113 

94 

80    . 

80 

75         100 

200 

150 

125 

100 

150 

125 

100 

100 

100         125 

250 

188 

156 

125 

188 

156 

125 

125 

125         150      ' 

300 

225 

188 

150 

225 

188 

150 

150 

150         175 

350 

263 

219 

175 

263 

219 

175 

175 

175         200 

400 

300 

250 

200 

300 

250 

200 

200 

200         225 

450 

338 

281 

225 

338 

281 

225 

225 

225         250 

500 

375 

313 

250 

375 

313 

250 

250 

250         275 

550 

413 

344 

275 

413 

344 

275 

275 

275         300 

600 

450 

375 

300 

450 

375 

300 

300 

300         325 

650 

488 

406 

325 

488 

406 

325 

325 

325         350 

700 

525 

438 

350 

525 

438 

350 

350 

350         375 

750 

563 

469 

375 

563 

469 

375 

375 

375         400 

800 

600 

500 

400 

600 

500 

400 

400 

Velocity 

feet  per  sec. 

2% 

4% 

5% 

6% 

1% 

2% 

4 

4 

Effective   area 

- 

of  register. 

1.00 

1.50 

1.83 

2.17 

1.00 

1.00 

1.33 

1.33 

Factor  for 

•Federal  Furnace  League  Handbook. 
fThe  Model  Boiler  Manual. 


352 


TABLE  22. 
Sheet    Metal    Dimensions    and    Weights. 


11 


Decimal 
gage 

Approximate 
millimeters 

Wt.  per  sq.  ft.  in  Ibs. 

U.  S.  gage 
numbers 

Iron 
480  Ibs.  per 
cu.  ft. 

Steel 
489.6  Ibs.  per 
cu.  ft. 

0.002 

0.05 

0.08 

0.082 

0.004 

0.10 

0.16 

0.163 

0.006 

0.15 

0.24 

0.245 

38-39 

0.008 

0.20 

0.32 

0.326 

34-35 

0.010 

0.25 

0.40 

0.408 

32 

0.012 

0.30 

0.48 

0.490 

30-31 

0.014 

0.36 

0.56 

0.571 

29 

0.016 

0.41 

0.64 

0.653 

27-28 

0.018 

0.46 

0.72 

0.734 

26-27 

0.020 

0.51 

0.80 

0.816 

25-26 

0.022 

0.56 

0.88 

0.898 

25 

0.025 

0.64 

1.00 

1.020 

24 

0.028 

0.71 

1.12 

1.142 

23 

0.032 

0.81 

1.28 

1.306 

21-22 

0.036 

0.91 

1.44 

1.469 

20-21 

0.040 

1.02 

1.60 

1.632 

19-20 

0.045 

1.14 

1.80 

1.836 

18-19 

0.050 

1.27 

2.00 

2.040 

18 

0.055 

1.40 

2.20 

2.244 

17 

0.060 

1.52 

2.40 

2.448 

16-17 

0.065 

1.65 

2.60 

2.652 

15-16 

0.070 

1.78 

2.80 

2.856 

15 

0.075 

1.90 

3.00 

3.060 

14-15 

0.080 

2.03 

3.20 

3.264 

13-14 

0.085 

2.16 

3.40 

3.468 

13-14 

0.090 

2.28 

3.60 

3.672 

13-14 

0.095 

2.41 

3.80 

3.876 

12-13 

0.100 

2.54 

4.00 

4.080 

12-13 

0.110 

2.79 

4.40 

4.488 

12 

0.125 

3.18 

5.00 

5.100 

11 

0.135 

3.43 

5.40 

5.508 

10-11 

0.150 

3.81 

6.00 

6.120 

9-10 

0.165 

4.19 

6.60 

6.732 

8-9 

0.180 

4.57 

7.20 

7.344 

7-8 

0.200 

5.08 

8.00 

8.160 

6-7 

0.220 

5.59 

8.80 

8.976 

4-5 

0.240 

6.10 

9.60 

9.792 

3-4 

0.250 

6.35 

10.00 

10.200 

3 

For  weights  of  galvanized  iron,  multiply  weight,  black,  by:— 
No.  28          No.  26          No.  24          No.  22          No.  20          No.  18          No.  16 


1.25 


1.21 


1.16 


1.07 


353 


TABLE   23. 


Weight  of  Round   Galvanized  Iron   Pipe   and   Elbows  of  the 
Proper    Gages    for    Heating    and    Ventilating    Work. 


•i 

Diam  of 
pipe 

ill 

£    '" 

.s 

fi 

53  c  o 

^  B«S 

°| 

!i 

OS'S  jy 

M 

O 

is 

=>'a 

ill 

.3  • 

Weight  per 
running 
foot 

-U  £ 

ll 

3 

9.43 

7.1 

0.7 

0.4 

36 

113.10 

1017.9 

17.2 

124.4 

4 

12.57 

12.6 

1.1 

0.9 

37 

116.24 

1075.2 

17.8 

131.4 

No.  28 

5 

15.71 

19.6 

1.2 

1.2 

38 

119.38 

1134.1 

18.2 

139.4 

0.78 

6 

18.85 

28.3 

1.4 

1.7 

39 

122.52 

1194.6 

18.7 

146.0 

7 

21.99 

38.5 

1.7 

2.3 

40 

125.66 

1256.6 

19.1 

152.9 

8 

25.13 

50.3 

1.9 

2.9 

No.  20 

41 

128.81 

1320.6 

19.6 

160.7 

1.66 

42 

131.95 

1385.4 

20.1 

168.6 

No.  26 
0.91 

9 
10 
11 
12 

28.27 
31.42 
34.56 
37.70 

63.6 
78.5 
95.0 
113.1 

2.4 
2.7 
2.9 
3.2 

4.3 
5.3 
6.4 
7.6 

43 
44 
45 
46 

135.09 
138.23 
141.37 
144.51 

1452.2 
1520.5 
1590.4 
1661.9 

20.6 
21.0 
21.5 
22.0 

176.7 
185.0 
193.4 
202.2 

13 

40.84 

132.7 

3.4 

8.9 

14 

43.98 

153.9 

3.7 

10.4 

15 

47.12 

176.7 

4.5 

13.5 

47 
48 

147.65 
150.80 

1734.9 
1809.6 

29.2 
29.8 

274.3 
286.6 

16 

50.27 

201.1 

4.7 

15.1 

49 

153.94 

1885.7 

30.4 

298.8 

No.  25 

17 

53.41 

227.0 

5.0 

17.0 

50 

157.08 

1963.5 

31.0 

309.9 

1.03 

18 

56.55 

254.5 

5.3 

19.1 

51 

160.22 

2042.8 

31.6 

322.5 

19 

59.69 

283.5 

5.6 

21.4 

No.  18 

52 

163.36 

2123.7 

32.2 

335.1 

20 

62.83 

314.2 

6.0 

23.9 

2.16 

53 

166.50 

2206.2 

33.0 

349.7 

54 

169.65 

2290.2 

S3.  6 

463.4 

No.  24 
1.16 

21 

22 
23 
24 
25 

65.97 
69.12 
72.26 

75.40 
78.54 

346.4 
380.1 
415.5 
452.4 
490.9 

7.0 
7.3 
7.7 
8.0 
8.3 

29.6 
32.3 
35.6 
38.6 
41.7 

55 
56 
57 
58 
59 
60 

172.79 
175.93 
179.07 
182.21 
185.35 
188.50 

2375.8 
2463.0 
2551.8 
2642.1 
2734.0 
2827.4 

34.4 
34.9 
35.6 
36.1 
36.7 
37.4 

377.2 
390.7 
405.1 
418.8 
433.1 
448.6 

26 

81.68 

530.9 

8.7 

45.1 

27 

84.82 

572.6 

10.9 

59.1 

28 

87.97 

615.7 

11.4 

64.2 

61 

191.64 

2922.5 

46.7 

569.7 

29 

91.11 

660.5 

11.8 

68.6 

62 

194.78 

3019.1 

47.5 

589.0 

No.  22 

30 

94.25 

706.9 

12.2 

73.4 

63 

197.92 

3117.3 

48.3 

608.6 

1.41 

31 

97.39 

754.8 

12.6 

78.3 

No.  16 

64 

201.06 

3217.0 

49.1 

628.5 

32 

100.53 

804.3 

13.0 

83.4 

2.66 

66 

207.34 

3421.2 

50.5 

666.6 

33 

103.67 

855.3 

13.5 

88.9 

68 

213.63 

3631.7 

52.1 

708.6 

34 

106.84 

907.9 

13.9 

94.3 

70 

219.91 

3848.5 

53.6 

750.4 

35 

109.96 

962.1 

14.3 

99.9 

72 

226.19 

4071.5 

55.1 

793.4 

354 


TABLE  24. 

Specific  Heats,  Coefficients  of  Expansion,  Coefficients  of  Trans- 
mission, and  Kusing-Points  of  Solids,  Liquids  or  Gases.41 


SUBSTANCE 

« 

is 

£g 

c»  .q 

Coefficient  of 
expansion 

Coefficient  of 
transmission 

Fusion  points, 
degrees 

Antimony 

0.0508 

00000602 

00022 

815 

Copper 

0.0951 

.00000955 

00404 

1949 

Gold    _. 

0.0324 

.00001060 

1947 

Wrought   iron 

0.1138 

.00000895 

.00089 

2975 

Glass     

0.1937 

.00000478 

.0000008 

1832 

Cast  iron  __      ._ 

0.1298 

.00000618 

.000659 

2192 

Lead 

0.0314 

00001580 

00045 

621 

Platinum 

0.0324 

.00000530 

3452 

Silver    _ 

0.0570 

.00001060 

00610 

1751 

Tin 

0.0562 

.00001500 

.00084 

446 

Steel   (soft)   . 

0.1165 

.00000600 

.00062 

2507 

Steel    (hard)    

0.1175 

.00000689 

.00034 

2507 

Nickel   steel  36% 

00000003 

Zinc 

0.0956 

00001633 

.00170 

787 

Brass 

0.0939 

.00001043 

.00142 

1859 

Ice 

0.5040 

.00000375 

.000024 

32 

Sulphur    ^_    __    

0.2026 

.00006413 

Charcoal  

0.2410 

.00007860 

.000002 

Aluminum    
Phosphorus 

0.1970 

0.1887 

.00002313 
.00012530 

.00203 

1213 

Water 

1.0000 

.00008806 

.000008 

Mercury  

0.0333 

.00003333 

.00011 

Alcohol   (absolute  )— 

0.7000 

.00015151 

.000002 

—  - 

Con- 
stant 
pres- 
sure 

Con- 
stant 
volume 

Coefficient 
of  cubical  ex- 
pansion at  1 
atmos. 

Air 

0  23751 

0  16847 

003671 

0000015 

Oxygen 

0  21751 

0  15507 

003674 

.0000012 

Hydrogen  _ 

3.40900 

2.41226 

003669 

.0000012 

Nitrogen    ._  . 

0.24380 

0.17273 

.003668 

.0000012 

Superheated  steam  . 

0.4805 

0.346 

.003726 

Carbonic  acid 

0.2170 

0.1535 

00000122 

*Kent  and  Suplee. 


355 


TABLE   25. 


Pressure,     in     Ounces,     per     Square     Inch,     Corresponding     to 
Various    Heads   of   Water,   in   Inches.* 


Decimal  parts  of  an  inch 

Head 

in 

.0 

.1 

.2 

.3 

.4 

.5 

.6 

.7 

.8 

.9 

inches 

0 

.06 

.12 

.17 

.23 

.29 

.35 

.40 

.45 

.52 

1 

.68! 

.63 

.69 

.75 

.81 

.87 

.93 

.98 

1.04 

1.09 

2 

1.16 

1.21 

1.27 

1.33 

1.39 

1.44 

1.50 

1.56 

1.62 

1.67 

3 

1.73 

1.79 

1.85 

1.91 

1.96 

2.02 

2.08 

2.14 

2.19 

2.25 

4 

2.31 

2.37 

2.42 

2.48 

2.54 

2.60 

2.66 

2.72 

2.77 

2.83 

5 

2.89 

2.94 

3.00 

3.06 

3.12 

3.18 

3.24 

3.29 

3.35 

3.41 

6 

3.47 

3.52 

3.58 

3.64 

3.70 

3.75 

3.81 

3.87 

3.92 

3.98 

7 

4.04 

4.10 

4.16 

4.22 

4.28 

4.33 

4.39 

4.45 

4.50 

4.56 

8 

4.62 

4.67 

4.73 

4.79 

4.85 

4.91 

4.97 

5.03 

5.08 

5.14 

9 

5.20 

5.26 

5.31 

5.37 

5.42 

5.48 

5.54 

5.60 

5.66 

5.72 

TABLE  26. 

Height  of  Water  Column,  in  Inches,  Corresponding  to  Pres- 
sures,  in   Ounces,   per   Square   Inch.* 


Decimal  parts  of  an  ounce 

Pressure 
in  ounces 

per  square 

.0 

.1 

.2 

.3 

.4 

.5 

.6 

.7 

.8 

.9 

inch 

0 

.17 

.35 

.52 

.69 

.87 

1.04 

1.21 

1.38 

1.56 

1 

"I"73 

1.90 

2.08 

2.25 

2.42 

2.60 

2.77 

2.94 

3.11 

3.29 

2 

3.46 

3.63 

3.81 

3.98 

4.15 

4.33 

4.50 

4.67 

4.84 

5.01 

3 

5.19 

5.36 

5.54 

5.71 

5.88 

6.06 

6.23 

6.40 

6.57 

6.75 

4 

6.92 

7.09 

7.27 

7.44 

7.61 

7.79 

7.96 

8.13 

8.30 

8.48 

5 

8.65 

8.82 

9.00 

9.17 

9.34 

9.52 

9.69 

9.86 

10.03 

10.21 

6 

10.38 

10.55 

10.73 

10.90 

11.07 

11.26 

11.43 

11.60 

11.77 

11.95 

7 

12.11 

12.28 

12.46 

12.63 

12.80 

12.97 

13.15 

13.32 

13.49 

13.67 

8 

13.84 

14.01 

14.19 

14.36 

14.53 

14.71 

14.88 

15.05 

15.22 

15.40 

9 

15.57 

15.74 

15.92 

16.09 

16.26 

16.45 

16.62 

16.76 

16.96 

17.14 

"Suplee's  M.  E.  Reference  Book. 


356 


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357 


TABLE  28. 
Expansion  of  Wrought-Iron  Pipe  on  the  Application  of  Heat.41 


Temp,  air 

when 

pipe 

is  fitted 


Increase  in  length  in  inches  per  100  feet 
when  heated  to 


Deg.  F. 

160 

180 

200 

212 

220 

228 

240 

274 

0 

1.28 

1.44 

1.60 

1.70 

1.76 

1.82 

1.93 

2.19 

32 

1.02 

1.18 

1.34 

1.44 

1.50 

1.57 

1.66 

1.94 

50 

.88 

1.04 

1.20 

1.30 

1.36 

1.42 

1.52 

1.79 

70 

.72 

.88 

1.04 

1.14 

1.20 

1.26 

1.36 

1.63 

TABLS  29. 
Tapping   List   of  Direct   Radiators.! 

STEAM. 


ONE-PIPE   WORK. 

TWO-PIPE    WORK. 

Radiator  area 
square  feet 

Tapping  diam- 
eter —  inches 

Radiator  area 
square  feet 

Tapping  diam- 
eter —  inches 

0—24 
24—60 
60  —  100 
100  and  above 

1 
1U 

¥ 

0—48 
48  —  96 
96  and  above 

1    x  % 
l%xl 
l&tfK 

WATER. 
Tapped  for  supply  and  return. 

Radiator  area 
square  feet 

Tapping  diameter 
inches 

0  —  40 
40  —  72 
72  and  above. 

1 

'Holland  Heating  Manual. 
tAmerican  Radiator  Co. 


358 


TABLE  30. 
Pipe  Equalization. 


(See  also  Table  19) 


This  table  shows  the  relation  of  the 
combined  area    of    small   round   warm 
air  ducts  or  pipes  to  the  area  of  one 
large  main  duct. 

The  bold  figures  at  the  top  of  the 
column  represent  the  diameters  of 
the  small  pipes  or  ducts;  those  in 
the    left-hand    vertical    columns 
are  the  diameters  of  the  main 
pipes.     The  small  figures  show  ^ 

the  number  of  small  pipes  that  Br- 

each main  duct  will  supply. 

Example.— To  supply  sixteen 
10-inch  pipes:    Refer  to  column 
having    10    at    top;     follow 
down    to    small    figure   16, 
thence  left    on  the  hori- 
zontal line  of  the  bold- 
face    figure     in     the 
outside  column,  and 
we  find   that   one 
30-inch  main  will 

supply  air  for  j; 

the  sixteen 
10  -  inch 
pipes. 


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359 


TABLE  31. 


Capacities    of   Hot    Water    Risers    in    Square    Feet    of   Direct 
Radiation.* 

Drop  in  temperature  20°. 


D.    of 

riser 
inches 

First 
floor 

Second 
floor 

Third 
floor 

Fourth 
floor 

Fifth 
floor 

Sixth 
floor 

% 

12 

17 

21 

24 

1 

22 

32 

40 

48 

lU 

38 

56 

70 

80 

88 

ll/2 

66 

92 

112 

1C2 

145 

2 

140 

196 

238 

2SO 

310 

2*/2 

240 

328 

400 

470 

515 

3 

3V& 
4 

350 
510 

700 

490 
705 
980 

595 
860 
1190 

703 
1010 
1280 

770 
1110 
1540 

8oO 
1215 
1660 

A  small  pipe  should  never  be  run  to  a  great  height  where  it 
only  supplies  one  radiator.  It  is  better  to  have  limits  for  pipes 
as  follows: 


D.   in  inches: 

Height   in   feet: 


1V4 

45 


(Reduce    size    by 
floors.) 


TABLE  32. 
Capacities  of  Pipes  in  Square  Feet  of  Direct  Steam  Radiation.f 


a 

i  i 

i 

B 

*0 

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s  : 

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lil 

• 
3 

c* 

IA 

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111 

.a 

1 

1 

i 

36 

60 

5 

3V2 

3720 

6200 

114 

i 

72 

120 

6 

6000 

10000 

1% 

i% 

120 

SCO 

7 

4 

9000 

15COO 

2 

280 

480 

8 

4 

12800 

21600 

2^ 

2  2 

528 

880 

9 

4'/2 

17800 

30000 

3 

2V2 

900 

1500    i 

10 

5 

23200 

39003 

3V2 

2% 

1320 

2200 

12 

6 

37000 

62000 

4 

3 

1920 

3200    | 

14 

7 

54000 

92COO 

3 

2760 

4600 

16 

8 

76000 

130000 

•International  Correspondence  School, 
t Kent 's  M.  E.  Poc.,et-Book. 


360 


TABLE  33. 

Capacities  of  Hot  \Vater  Pipes  in  Square  Feet  of  Direct 
Radiation.* 


Diameter 
of  pipes, 
inches 

Indi- 
rect 
radi- 
ation 

Direct  radiation. 
Height  of  coil  above  bottom  of  boiler,  in  ft. 

0 

TJ 

M 

30 

40 

50 

70 

100 

sq.  ft. 

sq.  ft. 

sq.  ft. 

sq.  ft. 

sq.  ft. 

sq.  ft. 

sq.  ft. 

sq.  ft. 

%  • 

49 

50 

52 

53 

55 

57 

61 

68 

1 

87 

89 

92 

95 

98 

101 

108 

121 

1V4 

136 

140 

144 

149 

153 

158 

169 

189 

1% 

196 

202 

209 

214 

222 

228 

243 

271 

2 

349 

359 

370 

380 

393 

405 

433 

483 

2^ 

546 

561 

577 

595 

613 

633 

678 

755 

3 

785 

•807 

835 

856 

888 

912 

974 

1083 

3V2 

1069 

1099 

1132 

1166 

1202 

1241 

1327 

1480 

4 

1395 

1436 

1478 

1520 

1571 

1621 

1733 

1933 

4V6 

1767 

1817 

1871 

1927 

1988 

2052 

2193 

2445 

5 

2185 

2244 

2309 

2376 

2454 

2531 

2713 

3019 

6 

3140 

3228 

3341 

3424 

3552 

3648 

3897 

4344 

7 

4276 

4396 

4528 

4664 

4808 

4964 

5308 

5920 

8 

5580 

5744 

5912 

6080 

6284 

6484 

6932 

7735 

9 

7068 

7268 

7484 

7708 

7952 

8208 

8774 

9780 

10 

8740 

8976 

9236 

9516 

9816 

10124 

10852 

12076 

11 

10559 

10860 

11180 

11519 

11879 

12262 

13108 

14620 

12 

12560 

12912 

13364 

13696 

14208 

14592 

15588 

17376 

13 

14748 

15169 

15615 

16090 

16591 

17126 

18307 

20420 

14 

17104 

17584 

18109 

18656 

19232 

19856 

21232 

23680 

15 

19634 

20195 

20789 

21419 

22089 

22801 

24373 

27168 

16 

22320 

22978 

23643 

24320 

25136 

25936 

27728 

30928 

TABLE  34. 

Capacities  of  Hot  \Vater  Mains  in  Square  Feet  of  Direct 
Hmliation.t 


Total  estimated  length  of  circuit 

D.  of 

mains 

100 

200 

300 

400 

500 

600 

700 

800 

900 

1000 

1 
1% 

20 
35 

20 

1H 

56 

40 

25 

2 

116 

85 

70 

50 

236 

220 

150 

120 

100 

90 

3 

345 

240 

200 

170 

150 

140 

125 

110 

100 

90 

3% 

500 

340 

280 

245 

225 

205 

190 

175 

162 

150 

4 

700 

485 

390 

340 

310 

280 

260 

240 

230 

220 

4V2 

925 

640 

535 

460 

410 

375 

345 

325 

300 

295 

5 

1200 

830 

700 

600 

540 

490 

450 

420 

400 

380 

6 

1900 

1325 

1100 

950 

850 

775 

700 

650 

620 

600 

7 

2000 

1600 

1400 

1250 

1140 

1050 

975 

925 

875 

8 

1970 

1720 

1550 

1440 

1350 

1300 

1250 

9 

1900 

1800 

1700 

1620 

"Kent's  M.  E.  Pocket-Book, 
international  Correspondence  School. 

361 


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364 


TABLE  38. 

Comparative  Sizes  of  Steam  Mains  and  Returns  for  Gravity 
and  Vaemim  Systems. 


Size  of 
supply 
pipe 

Size  of  return 

Size  of 
supply 
pipe 

Size  of  return 

Gravity 

Vacuum 

Gravity 

Vacuum 

% 

% 

4 

4 

VA 

1V2 

1 

% 

% 

4V2 

2V2 

Itf 

1% 

1 

y2 

5 

3 

2 

1% 

1% 

% 

6 

3% 

H4 

2 

l1^ 

% 

8 

IH 

3% 

2% 

2 

i 

10 

6 

4 

3 

2 

i1^ 

12 

6 

«H 

3y2 

2V2 

114 

14 

7 

5 

Note.— For  short  runs  of  piping  where  the  friction  is  not  a  serious 
matter  the  above  table  will  work  out  satisfactorily.  These  sizes  are 
only  approximate  and  should  be  used  with  caution. 


TABLE  39. 
Expansion    Tanks — Dimensions    and    Capacities.* 


Size  in  inches 

Capacity  gallons 

Sq.   ft.   of  radiation 

9x20 

5y2 

150 

10x20 

8 

250 

12x20 

10 

350 

12x24 

12 

450 

12x30 

15 

550 

12x36 

18 

650 

14x30 

20 

700 

14x36 

24 

850 

16x30 

26 

900 

16x30 

32 

1250 

16x48 

42 

1750 

18x60 

66 

2750 

20x60 

82 

4500 

22x60 

100 

6000 

24x60 

122 

7500 

*The  Model  Boiler  Manual. 


365 


TABLE  40. 
Sizes    of   Flanged    Fittings. 


All  fittings  and 
flanges 


90° 
elbow 


ft 


45° 
elbow 


Long 
turn 
elbow 


II 


Tee 


ss 


Cross 


Lateral 


ft 

Is 


19 


16 
19 
21 

23% 
27% 
32 


7% 
»H 

li% 
14% 
17 

21% 

25 

29% 


6% 

8 

9 
11 
12 
14 
15 
18 
22 


6 

7% 
7% 
8 

9% 
11 


6% 

8 

9 
11 
12 
14 
15 
18 
22 


12 

17% 
20% 

g" 

30 
35 
40% 


TABLE  41. 
Dimensions  of  Ells  and  Tees  for  Wrought  Iron  Pipe. 


SIZE 


2- 


4-l/» 

5- 

6- 


2-3^ 


3-^8 


-/8 


4- 


1- 

l-Vi 

n 


4- 
5-4 


2-H 
4-' 


6- 

6-% 

7-  7/» 


1- 


4- 

4-96 


366 


TABLE  42. 


Loss    of    Pressure    in    Pipes    100    Feet    Long:    in    Ounces    per 
Square  Inch  when  Delivering  Air  at  the  Velocities  Given. 


>»    a 

Ifl 

>.Sa 

Diameter  of  pipe  in  inches 

1 

2 

3 

4 

6 

8 

10 

12 

14 

16 

18 

300 
400 
600 
800 
1000 
1200 
1500 
1800 
2400 

300 
400 
600 
800 
1000 
1200 
1500 
1800 
2400 

0.100 
0.178 
0.400 
0.711 
1.111 
1.600 
2.500 
3.600 
6.400 

0.050 
0.088 
0.200 
0.356 
0.556 
0.800 
1.250 
1.800 
3.200 

0.033 
0.059 
0.133 
0.237 
0.370 
0.533 
0.833 
1.200 
2.133 

0.025 
0.044 
0.100 
0.178 
0.278 
0.400 
0.625 
0.900 
1.600 

0.017 
0.030 
0.067 
0.119 
0.185 
0.267 
0.417 
0.600 
1.067 

0.012 
0.022 
0.050 
0.089 
0.139 
0.200 
0.312 
0.450 
0  800 

0.010 
0.018 
0.040 
0.071 
0.111 
0.160 
0.250 
0.360 
0  640 

0.008 
0.015 
0.033 
0.059 
0.092 
0.133 
0.208 
0.300 
0.533 

6.007 
0.013 
0.029 
0.051 
0.079 
0.114 
0.179 
0.257 
0.457 

0.006 
0.011 
0.025 
0.044 
0.069 
0.100 
0.156 
0.225 
0.400 

0.006 
0.010 
0.022 
0.040 
0.062 
0.089 
0.139 
0.200 
0.356 

36 

0.003 
0.005 
0.011 

40 

0.002 
0.004 
0  010 

60 

0.002 
0.003 
0.007 

20 

24 

28 

32 

44 

48 

52 

56 

0.005 
0.009 
0  020 

0.004 
0.007 
0  017 

0.004 
0.006 
0.014 

0.003 
0.006 
0  012 

0.002 
0.004 
0  009 

0.002 
0.004 
0  008 

0.002 
0.003 
0  008 

0.002 
0.003 
0.007 

0  036 

0  029 

0.025 

0.022 

0.020 

0  018 

0  016 

0  015 

0.014 

0.013 

0.012 

0.056 
0.080 
0.125 
0.180 
0.320 

0.046 
0.067 
0.104 
!  0.167 
0.313 

0.040 
0.057 
0.089 
0.129 
0.239 

0.035 
0.050 
0.078 
0.112 
0.200 

0.031 
0.044 
0.069 
0.100 
0.178 

0.028 
0.040 
0.062 
0.090 
0.160 

0.025 
0.036 
0.057 
0.082 
0.145 

0.023 
0.033 
0.052 
0.075 
0.133 

0.021 
0.031 
0.048 
0.069 
0.123 

0.020 
0.029 
0.045 
0.064 
0.119 

0.019 
0.027 
0.042 
0.060 

0.107 

Diagrams  for  Pipe  Sizes  and  Friction  Heads. 

To  illustrate  the  use  of  the  two  following  diagrams,  ap- 
ply to  the  pipe  line,  B,  C,  Art.  147.  First,  let  I  =  1500  feet, 
d  =  8  inches  and  v  =•  5  feet  per  second.  Trace  along  the 
velocity  line  until  it  intersects  the  diameter  line,  then  fol- 
low the  ordinate  to  the  top  of  the  page  and  find  the  friction 
head,  13  feet  for  1000  foot  run  or  19.5  feet  for  the  1500  foot 
run.  Second,  let  Q  =  1.75  cubic  feet  per  second  and  d  =  8 
inches.  Trace  to  the  left  along  the  horizontal  line  represent- 
irg  the  volume  of  1.75  cubic  feet  until  it  intersects  the 
diameter  line,  then  read  up  and  find  the  same  friction  head 
as  before.  Third,  let  the  allowable  friction  head  for  1500. 
feet  of  main  be  19  feet,  when  Q  =  1.75  cubic  feet  per  second 
or  when  v  =  5  feet  per  second.  Reverse  the  process  given 
above  and  find  an  8  inch  pipe. 


367 


368 


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369 


TABLE  43. 
Temperatures   for   Testing   Direct    Steam   Radiation  Plants.* 


Test 
condi- 
tion 

Steam 
Tem- 
pera- 
ture 

Steam  pressure  intended  for  zero  weather 

Olb. 

1  Ib. 

2  Ib. 

3  Ib. 

4  Ib. 

5  Ib. 

6  Ib. 

7  Ib. 

8  Ib. 

9  Ib. 

10  Ib. 

10  in. 

192.0 

63.3 

62.3 

9    " 

194.5 

64.2 

63.2 

62.3 

8    " 

197.0 

65.0 

64.0 

63.0 

62.2 

7     " 

199.0 

65.6 

64.7 

63.7 

62.8 

62.0 

6     " 

201.0 

66.3 

65.3 

64.3 

63.4 

62.6 

62.0 

5     " 

203.0 

67.0 

66.0 

65.0 

64.0 

63.3 

62.6 

61.9 

4     " 

205.0 

67.6 

66.6 

65.6 

64.7 

63.9 

63.2 

62.5 

61.7 

3    " 

207.0 

68.3 

67.2 

66.2 

65.3 

64.5 

63.8 

63.1 

62.3 

61.7 

2     " 

208.5 

68.8 

67.7 

66.7 

65.7 

65.0 

64.2 

63.6 

62.8 

62.0 

61.5 

1     " 

210.5 

69.4 

68.3 

67.5 

66.4 

65.6 

64.8 

64.2 

63.3 

62.6 

62.1 

61.5 

0  Ib. 

212.0 

70.0 

68.8 

67.8 

66.9 

66.1 

65.3 

64.6 

63.8 

63.1 

62.6 

62.0 

1     " 

215.5 

71.2 

70.0 

68.0 

67.2 

66.3 

65.8 

65.0 

64.2 

63.7 

63.0 

2     " 

218.7 

72.1 

71.0 

7o!o 

69.2 

68.2 

67.3 

66.7 

65.9 

65.1 

64.5 

64.0 

3     " 

221.7 

72.0 

71.0 

70.0 

69.2 

68.3 

67.6 

66.7 

66.0 

65.4 

64.8 

4     " 

224.5 

71.8 

70.8 

70.0 

69.2 

68.4 

67.5 

66.7 

66.2 

65.7 

5     " 

227.2 

71.7 

70.8 

70.0 

69.2 

68.3 

67.6 

67.0 

66.3 

6     " 

229.8 

71.7 

70.8 

70.0 

69.2 

68.4 

67.7 

67.2 

7     " 

232.4 

71.7 

70.8 

70.0 

69.2 

68.6 

68.0 

8     " 

234.9 

71.7 

70.8 

70.0 

69.3 

68.7 

9     " 

237.3 

71.5 

70.5 

70.0 

69.3 

10     " 

239.4 

71.3 

70.7 

70.0 

Factors 

.670 

.675 

.678 

.684 

.688 

.692 

.694 

.698 

.702 

.705 

.707 

The  temperatures  in  this  table  are  for  a  plant  designed  for  0°  and  70°. 

Example.— It  is  desired  to  test  a  plant  designed  for  5  pounds  gage 
pressure  on  a  day  when  the  outside  temperature  is  22  degrees.  What 
should  be  the  temperature  in  the  rooms  with  steam  at  3  pounds  gage 
pressure?  It  will  be  noted  in  the  vertical  column  marked  5  pounds,  that 
opposite  the  3  pound  pressure  68.3  degrees  may  be  expected  on  a  zero 
day.  As  the  temperature  was  22  degrees  above  we  must  add  22  times 
.692,  or  15.2  degrees,  thus  making  a  total  of  83.5  degrees,  the  tempera- 
ture which  should  exist  indoors. 

*W.  W.  Macon. 


370 


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cu  rn  a,1"  n-.'S^  w  C 

S  O  g  O       a  O  °       - 


O1  C3  O"  *>        •--  .2  .S 
BOKtoM      MQOOQ 

371 


.  g 

W  §    g 

WW  S     < 


ote.— 
and  w 

ess  boi 
cturer 


TABLE  45. 

Percentage  of  Heat  Transmitted  by  Various  Pipe-Coverings, 

From  Tests  Made  at   Sibley  College,   Cornell   University, 

and   at    Michigan   University.* 

Relative  amount 
Kind   of  covering  of  heat 

transmitted 

Naked  pipe  100. 

Two  layers  asbestos  paper,  1  in.  hair  felt,  and  canvas 

cover 15.2 

Two    layers    asbestos    paper,    1    in.    hair    felt,    canvas 

cover  wrapped  with  manilla  paper 15. 

Two  layers  asbestos  paper,  1  in.  hair  felt 17. 

Hair  felt  sectional  covering,  asbestos  lined 18.6 

One  thickness  asbestos  board   59.4 

Four  thicknesses  asbestos  paper   50.3 

Two  layers  asbestos  paper 77.7 

Wool   felt,  asbestos  lined    23.1 

Wool  felt  with  air  spaces,  asbestos  lined 19.7 

Wool  felt,  plaster  paris  lined   .  .  • 25.9 

Astoestos  molded,  mixed  with  plaster  paris 31.8 

Asbestos  felted,  pure  long  fibre   20.1 

Asbestos  and  sponge 18.8 

Asbestos  and  wool  felt 20.8 

Magnesia,  molded,  applied  in  plastic  conditnon 22.4 

Magnesia,  sectional 18.8 

Mineral  wool,  sectional   19.3 

Rock   wool,   fibrous 20.3 

Rock   wool,    felted 20.9 

Fossil  meal,  molded,   %   inch  thick   29.7 

Pipe  painted  with  black  aephaltum 105.5 

Pipe  painted  with  light  drab  lead  paint 108.7 

Glossy  white   paint    95.0 

"Carpenter's  H.  and  V.  B. 

Note. — These  tests  agree  remarkably  well  with  a  series 
made  by  Prof.  M.  E.  Cooley  of  Michigan  University,  and  also 
with  some  made  by  G.  M.  Brill,  Syracuse,  N.  Y.,  and  reported 
in  Transactions  of  the  American  Society  of  Mechanical  En- 
gineers, vol.  XVI. 


372 


TABLE  46. 
Factors   of  Evaporation. 


Gage 

pressure 

.3 

10 

20 

30 

50 

100 

125 

135 

150 

175 

Peed 
water       , 

Factors  of  evaporation 

212 

1.0003 

1.0103 

1.0169 

1.0218 

1.0290 

1.0396 

1.0431 

1.0443 

1.0460 

1.0483 

200 

1.0127 

1.0227 

1.0293 

.0343 

1.04141.0520 

1.0555 

1.0567 

1.0584 

1.0608 

185 

1.0282 

1.0382 

1.0448 

.0498 

1.0569 

1.0675 

1.0710 

1.0722 

1.0739 

1.0763 

170 

1.0437 

1.0537 

1.0603 

1.0653 

1.0724 

1.0830 

1.0865 

1.0877 

1.0894 

1.0917 

155 

1.0592 

1.0692 

1.0758 

.0807 

1.0878 

1.0985 

1.1020 

1.1032 

1.1048 

1.1072 

140 

.0715 

1.0846 

1.0912 

1.0962 

1.1033 

1.1139 

1.1174 

1  1186 

1.1203 

1.1227 

125 

.0901 

1.1001 

1.1067 

1.1116 

1.1187 

1.1293 

1.1328 

1  1341 

1  .  1357 

1.1381 

110 

.1055 

1.1155 

1.1221 

1.1270 

1.1341 

1.1447 

1.1482 

I  1495 

1  1511 

1.1535 

95 

.1209 

1.1309 

1.1375 

1.1424 

1.1495 

1.1602 

1.1637 

1.1649 

1.1665 

1.1689 

80 

.1363 

1.1463 

1.1529 

1.1578 

1.1650 

1.1756 

1.1791 

1.1803 

1.1820 

1.1843 

65 

.1517 

1.1617 

1.1683 

1.1733 

1.1804 

1.1910 

1.1945 

1.1957 

1.1974 

1.1997 

50 

.1672 

1.1772 

1.1838 

1.1887 

1.1958 

1.2064 

1.2099 

1.2112 

1.2128 

1.2152 

35 

.1827 

1.1927 

1.1993 

1.2042 

1.2113 

1.2219 

1.2255 

1.2267 

1.2283 

1.2307 

TABLE  47. 

Per  Cent,  of  Total  Heat  of  Steam  Saved  per  Degree  Increase 
of  Feed  Water. 


Initial 
temp, 
of  feed 

Gage  pressure  in  boiler,  Ibs.  per  sq.  in. 

0 

20 

40 

60 

80 

ICO 

120 

140 

160 

180 

32 

.0872 

.0861 

.0855 

.0851 

.0847 

.0844 

.0841 

.0839 

.0837 

.0835 

40 

.0878 

.0867 

.0861 

.0856 

.0853 

.0850 

.0847 

.0845 

.0843 

.0839 

50 

.0886 

.0875 

.0868 

.0864 

.0860 

.0857 

.0854 

.0852 

.0850 

.0846 

60 

.0894 

.0883 

.0876 

.0872 

.0867 

.0864 

.0862 

.0859 

.0856 

.0853 

70 

.0902 

.0890 

.0884 

.0879 

.0875 

.0872 

.0869 

.0867 

.0864 

.0860 

80 

.0910 

.0898 

.0891 

.0887 

.0883 

.0879 

.0877 

.0874 

.0872 

.0868 

100 

.0927 

.0915 

.0908 

.0903 

.0899 

.0895 

.0892 

.0890 

.0887 

.0883 

120 

.0945 

.0932 

.0925 

.0919 

.0915 

.0911 

.0908 

.0906 

.0903 

.0899 

140 

.0963 

.0950 

.0943 

.0937 

.0932 

.0929 

.0925 

.0923 

.0920 

.0916 

160 

.0982 

.0968 

.0961 

.0955 

.0950 

.0946 

.0943 

.0940 

.0937 

.0933 

180 

.1002 

.0988 

.0981 

.0973 

.0969 

.0965 

.0961 

.0958 

.0955 

.0951 

200 

.1022 

.1008 

.0999 

.0993 

.0988 

.0984 

.0980 

.0977 

.0974 

.0969 

220 



.1029 

.1019 

.1013 

.1008 

.1004 

.1000 

.0997 

.0994 

.0989 

240 



.1050 

.1041 

.1034 

.1029 

.1024 

.1020 

.1017 

.1014 

.1009 

Example.— Boiler  pressure  120  Ibs.  gage,  initial  temperature  of  feed 
water  60  deg.,  heated  to  210  deg.  Then  increase  in  temperature  150, 
times  tabular  figure,  .0862,  equals  12.93  per  cent,  saving. 


373 


374 


TABLE  49. 

Steam    Consumption    of    Various    Types    of    Non-Condensing 

(Approximate). 


Pounds  per  indicated  horse-power  hour. 


oj 

s 

l!§ 

Is 

a 
o 
o 

1-1     —  < 

3         03 

53S 

||| 

tn 

q  >3 

IP. 

(£  « 

"3,  h  J3 

"S-"  "* 

"3.5^ 

rs  «  '" 

a    ^.Q  "3 

ft          W  ,jQ  "3 

ft     ^  ^"a 

1! 

.§•3^ 

53  a!§ 

111 

111 

Illfi 

oils! 

10 

52 

20 

50 

40.0 

30 

49 

39.0 

40 

48 

38.0 

50 

48 

38.0 

34.5 

35.0 

60 

47 

36.0 

32.5 

33.0 

70 

47 

35.0 

31.5 

32.0 

80 

46 

34.0 

30.5 

31.0 

90 

45 

33.0 

29.5 

30.0 

100 

45 

32.0 

28.5 

29.0 

150 

44 

31.5 

28.0 

28.5 

22.5-23 

21.5-22 

21-21.5 

200 

43 

30.5 

27.0 

27.5 

22-22.5 

21-21.5 

90.5-21 

250 

43 

30.0 

26.5 

27.0 

22-22.5 

21-21.5 

20-20.5 

300 

42 

29.0 

25.5 

26.0 

22-22.5 

20.5-21 

20-20.5 

400 

41 

28.5 

25.0 

25.5 

21.5-22 

20-20.5 

19.5-20 

500 

.41 

28.5 

25.0 

25.5 

20-21.5 

19.5-20 

19-19.5 

The  foregoing  table  was  compiled  principally  from  the  records  of  a 
large  number  of  actual  tests  of  engines  of  various  makes,  under  reason- 
ably favorable  conditions.  It  is  based  upon  the  actual  weight  of  con- 
densed exhaust  steam. 

*Atlas  Engine  Works  Catalog. 


37B 


TABLE  50. 

Speeds,  Capacities  and  Horse-Powers  of  "Green"  Steel  Plate 
Fans   at   Varying   Pressures.* 


II 

of 

Pressures 

.26  in. 

.87  in. 

1.3  in. 

1.7  in. 

2.2  in. 

2.6  in. 

3.02  in. 

3.46  in. 

4.33  in. 

%  oz. 

Vz  oz. 

%  oz. 

1  oz. 

1*4  oz 

iVz  oz 

1%  oz. 

2  OZ. 

2Y2  oz. 

CU.  FT. 

2249 

3176 

3891 

4498 

5029 

5513 

5956 

6372 

7135 

30 

R.  P.  M. 

330 

466 

571 

660 

738 

809 

874 

935;   1047 

H.  P. 

.286 

.811 

1.491 

2.298 

3.213 

4.227 

5.311 

6.515;  9.120 

CU.  FT. 

3239 

4581 

5605 

6477 

7242 

7937 

8584 

9173 

10268 

36 

R.  P.  M. 

275 

389 

476 

550 

615 

674 

729 

779 

872 

H.  P. 

.413 

1.170 

2.148 

3.311 

4.625 

6.086 

7.681 

9.375 

13.125 

CU.  FT. 

4398 

6214 

7617 

8815 

9864 

10799 

11679 

12483 

13981 

42 

R.  P.  M. 

235 

332 

407 

471 

527 

577 

624 

667 

747 

H.  P. 

.557 

1.576 

2.898 

5.473 

6.300 

8.287 

10.450 

12.750 

17.825 

CU.  FT. 

5750 

8123 

9937 

11500 

12867 

14123 

15240 

16301 

18282 

48 

R.  P.  M. 

206 

291 

356 

412 

461 

506 

546 

584 

655 

H.  P. 

.733 

2.076 

3.810 

5.880 

8.223 

10.832 

13.636 

16.670 

23.370 

CU.  FT. 

7602 

10758 

13167 

15203 

17030 

18650 

20145 

21558 

24174 

54 

R.  P.  M. 

183 

259 

317 

366 

410 

449 

485 

519 

582 

H.  P. 

.970 

2.750 

5.047 

7.767 

10.880 

14.300 

18.0:7 

21.992 

30.896 

CU.  FT. 

9715 

13718 

16780 

19429 

21725 

23786 

25728 

27495 

30792 

60 

R.  P.  M. 

165 

233 

285 

330 

369 

404 

437 

467 

523 

H.  P. 

1.241 

3.506 

6.433 

9.932 

13.882 

18.230 

22.996 

28.077 

39.355 

CU.  FT. 

12078 

17071 

20855 

24156 

26975 

29551 

32047 

34221 

38247 

66 

R.  P.  M. 

150 

212 

259 

300 

335 

367 

398 

425 

475 

H.  P. 

1.542 

4.361 

7.996 

12.352 

17.238 

22.666 

28.675 

35.123 

48.895 

CU.  FT. 

15608 

21942 

26918 

31103 

34835 

38115 

41169 

44109 

49312 

72 

R.  P.  M. 

138 

194 

238 

275 

308 

337 

364 

390 

436 

H.  P. 

1.983 

5.601 

10.322 

15.881 

22.252 

29.223 

36.808 

45.043 

62.783 

CU.  FT. 

20192 

28405 

34907 

40383 

45174 

49452 

53387 

57152 

63996 

84 

R.  P.  M. 

118 

166 

204 

236 

264 

289 

312 

334 

374 

H.  P. 

2.581 

7.262 

13.387 

20.650 

28.875 

37.931 

47.775 

58.450 

81.812 

CU.  FT. 

23008 

32614 

39762 

46016 

51601 

56515 

60983 

65227 

73045 

86 

R.  P.  M. 

103 

146 

178 

206 

231 

253 

273 

292 

327 

H.  P. 

2.941 

8.337 

15.261 

23.531 

32.982 

43.348 

54.511 

66.707 

93.380 

CU.  FT. 

29260 

41027 

50568 

58519 

65198 

71559 

77284 

82690 

92549 

108 

R.  P.  M. 

92 

129 

159 

184 

205 

225 

243 

260 

291 

H.  P. 

3.737 

10.488 

19.397 

30.060 

41.666 

54.871 

69.163 

84.556 

118.291 

CU.  FT. 

36209 

51042 

62384 

71982 

80270 

88559 

95539 

102083 

114298 

120 

R.  P.  M. 

83 

117 

143 

165 

184 

203 

219 

234 

262 

H.  P. 

4.628 

13.050 

23.925 

36.807 

51.307 

67.928 

85.495 

104.401 

146.116 

CU.  FT. 

43560 

61565 

75504 

87120 

97575 

106868 

115580 

123711 

138231 

132 

R.  P.  M. 

75 

106 

130 

150 

168 

184 

199 

213 

238 

H.  P. 

5.568 

15.730 

28.957 

44.550 

62.370 

82.096 

103.430 

126.521 

176.715 

CU.  FT. 

52026 

73138 

89726 

103298 

116116 

127426 

137228  147030 

164372 

144 

R.  P.  M. 

69 

97 

119 

137 

154 

169 

182    195 

218 

H.  P. 

6.65 

18.700 

34.411 

52.822 

74.221 

97.741 

1?"  802 

150.  3"^ 

210.133 

! 

i 

Manufacturer's  Note.— The  horse-power  required  to  drive  a  fan 
will  vary  according  to  the  manner  of  application.  The  horse- 
powers given  above  are  25  per  cent,  greater  than  would  be  required 
under  ideal  conditions. 

"Condensed  from  the  G.  F.  E.  Co.  Catalog. 


376 


TABLE  51. 

Speeds,  Capacities  and  Horse-Powers  of  «A.  B.  C."  Steel 
Plate  Fans  at  Varying  Pressures.* 


s 

rtS 
ca  3 
P^X 

Diam.  of 
wheel 

Static 
press. 

w 

1" 

IVs" 

2" 

2V2" 

3" 

B%? 

4" 

.29 
oz. 

.58 
OZ. 

.87 
oz. 

1.16 
oz. 

1.44 
oz. 

1.73 

OZ. 

2.02 
OZ. 

2.31 
OZ. 

50 

30 

C.  F.  M. 
B.  P.  M. 
B.  H.   P. 

38401     54251     66401     7650)     8595 
471        665       816       945      1060 
.88|    2.481    4.551    7.00|     9.81 

9400 
1150 
12.85 

10110]  10810 
1250     1330 
16.20|  19.75 

60 

36 

C.   F.   M. 

n.  P.  M. 

B.   H.  P. 

5475]    7740 
393       555 
1.251    3.53 

9460 
681 
6.49 

109001  12250 
9.94|  14.00 

13400 
961 
18.35 

14410 
1040 
23.10 

i  15420 
1110 
28.10 

70 

42 

C.   F.   M. 
B.  P.  M. 
B.   H.   P. 

7100 
336 
1.62 

10020 
475 
4.58 

12280 
583 
8.35 

14150 
675 
12.93 

15900 
755 
18.19 

!  17400 
825 
23.80 

18700 
890 
29.90 

120010 
9:0 
36.60 
24350 
832 
44.50 

80 

48 

C.   F.  M. 
B.   P.   M. 
B.  H.  P. 

8640 
294 
1.97 

12200 
416 
5.57 

14950)  17200 
511        590 
10.20|  15.71 

19350 
660 
22.10 

121150 
722 
28.90 
26950 
641 
36.85 

22800 
36.50 

90 

54 

C.   F.  M. 
B.   P.   M. 
B.   H.   P. 

11000 
262 
2.52 

15540]  190001  21900 
370       454       525 
7.081  13.001  20.00 

24600 
587 
28.10 
"31450 
529 
35.95 

29000]  31003 
C93       740 
46.40]  56.50 

100 

.60 

C.   F.  M. 
B.  P.  M. 
B.   H.   P. 

140501  19850 
236       333 
3.2l|    9.05 

24300 
409 
16.65 

371 
19.70 

28000 
473 
25.60 

i  34400 
578 
47.10 

37000 
625 
59.10 

139600 
665 
72.30 

110 

66 

C.  F.  M. 
B.  P.  M. 
B.   H.   P. 

16600 
214 
3.80 

23500 
303 
10.75 

33100 
430 
30.25 

37200 
480 
42.50 

40700 
525 
55.60 

43800 
668 

70.00 

46900 
605 
85.60 

120 

72 

C.  F.  M. 
B.  P.  M. 
B.   H.   P. 

328700 
278 
13.10 

35100]  40500 
340       394 
24.001  37.00 
474001  54500 
292       337 
32.40|  49.80 

45500 
440 
52.00 

49700 
481 
68.00 

357300 
555 
104.50 

140 

84 

C.   F.  M. 
B.   P.   M. 
B.  H.   P. 

27400 
168 
6.25 

38700 
238 
17.75 
1~48900 
208 
22.30 

61300 
378 
70.00 

67000 
413 
91.70 

72200 
445 
115.20 

77250 
475 
140.9 
97500 
416 
178.0 

'    160 
180 

96 

C.  F.  M. 
E.   P.  M. 
B.  H.   P. 

34500 
147 

7.88 

59800 
256 
41.00 

68900 
296 
62.90 
85000 
262 
77.60 
103000 
236 
93.50 
122200 
214 
111.50 

77300 
331 
88.40 

84500 
362 
115.5 

91000 
390 
145.4 

108 

C.  F.  M. 
B.  P.  M. 
B.   H.   P. 

42600 
131 
9.75 

60300 
185 
.  27.55 
73000 
166 
33.30 

73800 
227 
50.50 

95500 
293 
109.0 

104300]  112500]  120000 
320       346       369 
143.01  180.01  219.0 

200 

120 

C.  F.   M. 
B.  P.  M. 
B.  H.  P. 

51600 
118 
11.8 

204 
61.20 

115700 
264 
132.1 

126500 
289 
173.0 

136100 
312 
217.50 
162000 
283 
259.0 

145800 
332 
?66.0 

220 

132 

C.   F.  M. 
B.   P.  M. 
B.   H.   P. 

614001  868001106000 
107       151       185 
14.01  39.60[  72.50 

137400]  150200 
240       262 
157.01  206.0 

173003 
302 
316.0 

240 

144 

C.  F.   M. 
B.   P.  M. 
B.   H.   P. 

72000 
98 
16.5 

101800 
139 
46.50 

124500 
170 
85.00 

143500]  161000]  176000]  1895001  203000 
197       220       241        260       377 
131.001  184.  Ol  241.01  303.  0[  370.5 

Manufacturer's  Note.— Any  of  the  above  fans,  when  running  at  the 
speed  and  pressure  indicated,  will  deliver  the  volume  of  air  and  require 
no  more  power  than  given  in  the  table. 

Allowances  must  be  made  for  the  inefficiency  of  the  motive  power 
and  for  transmission  losses  between  motive  power  and  the  fan. 

*0ondensed  from  the  A.  B.  C.  Co.  Catalog. 

377 


TABLE  52. 

Speeds,    Capacities   and   Horse-Powers   of 
Varying  Pressures.* 


'Sirocco"   Pans   at 


G  S 
eg  3 

o 

Pressures 

in. 

1 
in. 

int 

iy2 

in. 

2 

in. 

2% 
in. 

3 

in. 

sy2 

in. 

4 

in. 

.43 
oz. 

.58 
oz. 

.72 
oz. 

.87 
oz. 

1.16 
oz. 

1.44 
oz. 

1.73 
oz. 

2.02 
oz. 

2.31 
oz. 

4 

24 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

4260 
391 
.879 

4920 
453 
1.348 

5500 
505 
1.89 

6020 
554 
2.475 

6945 
640 
3.8 

7770 
714 
5.32 

8520 
783 
7.00 

9200 
846 
8.825 

9840 
905 
10.77 

5 

30 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

6650 
313 
1.37 

7690 
362 
2.105 

8600 
403 
2.96 

9416 
443 
3.868 

10870 
512 
5.95 

12150 
571 
8.315 

13320 
625 
10.94 

14380 
676 
13.80 

15380 
724 
16.85 

6 

36 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

9580 
260 
1.975 

11060 
302 
3.03 

12350 
336 
4.25 

13540 
369 
5.563 

156301  17470 
427       477 
8.56!  11.96 

191501  206SO 
523       565 
15.72|  19.85 

22150 
604 
24.23 

7 

42 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

13050 
223 
2.69 

15070 
259 
4.126 

16800 
288 
5.78 

18425 
316 
7.565 

21260 
366 
11.66 

23800]  26100 
408       447 
16.28'  21.43 

28200 
.   483 
27.06 

30140 
517 
33 

8 

48 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

17000 
196 
3.51 

19700 
226 
5.39 

22000 
252 
7.58 

241001  27820 
277       320 
9.9|  15.22 

31100 
358 
21.30 

340801  36800 
392       424 
28.  Ol     35.3 

39370 
453 
43.15 

9 

54 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

21500 
174 
4.43 

24860 
201 
6.81 

27800 
224 
9.57 

30440 
246 
12.52 

35140 
285 
19)23 

39300 
317 
2§.94 

431001  466001  49803 
348       3Y6       402 
35.3S|  44.70|     54.5 

10 

60 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

26500 
156 
5.46 

30750 
181 
8.42 

34300 
202 
11.8 

37650 
222 
15.47 

43400 
256 
23.77 

485701  53220 
286       313 
33.231  43.72 

57500 
338 
55.2 

61500 
362 
67.4 

11 

66 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

32200 
142 
6.65 

37200 
165 
10.18 

41500 
184 
14.3 

45530 
202 
18.72 

52550 
233 
28.77 

58830!  64450 
260       285 
40.24!     52.9 

6963 
308 
66.85 

74400 
329 
81.5 

12 

72 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

38300]  44240 
130       151 
7.9!  12.11 

49400 
168 
17 

54130]  62500 
185       214 
22.251     34.2 

69900 
238 
47.85 

76600 
261 
63 

828CO 
282 
79.5 

88500 
302 
97 

13 

78 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

45000 
120 
9.28 

52000 
140 
14.22 

58100 
155 
20 

63600 
171 
26.16 

73500]  82100 
197       220 
40.221     56.2 

90000I  97300 
241        261 
741  93.35 

104003 
279 
113.9 

14 

84 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

52100]  602001  67300 
112       130       144 
10.751   !6.49l    23.2 

73700 
158 
30.3 

85000]  95000 
183       204 
46.61        65 

104200 
224 
85.6 

112700 
242 
108 

120400 
259 
132 

15 

90 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

59900]  69230 
104        121 
12.341   18.93 

77500 
135 
26.6 

847001  97800]  109200 
148       171        191 
34.81  53.551    74.9 

1198001129600 
209       226 
98.  51  124.2 

138500 
212 
151.7 

16 

96 

C.  F.  M. 
R.  P.  M. 
B.  H.  P. 

67950 
98 
13.98 

78430 
114 
21.5 

81800 
126 
30.2 

96140 
139 
39.6 

1143001124500 
160       178 
63|    85.7 

1360001147000 
196       211 

1121      142 

157330 
226 
173 

'Condensed  from  A.  B.  C.  Co.  Catalog. 


378 


APPENDIX  II 


References  used  Chiefly  in  Refrigeration 
and  Ice  Production 


379 


TABLE  53. 
Freezing  Mixtures.* 


Names  and  proportions  of  ingredients 
in  parts 


Reduction  of 
temp.  deg.  F. 


From       To 


Total 
Reduc- 
tion of 

temp, 
deg.  F. 


Snow  or  pounded  ice  2;  sodium  chloride  1 

Snow  5;  sodium  chloride  2;  ammonium  chloride  1 
Snow  12;  sodium  chloride  5;  ammonium  nitrate  5 

Snow  8;  calcium  chloride  5 

Snow  2;  sodium  chloride  1 

Snow  3;  dilute  sulphuric  acid  2 

Snow  3;  hydrochloric  acid  5 

Snow  7;  dilute  nitric  acid  4 

Snow  3;  potassium  4 

Ammonium  chloride  5;  potassium  nitrate  5; 

water  16 

Ammonium  nitrate  1;  water  1 

Ammonium  chloride  5;  potassium  nitrate  5; 

sodium  sulphate  8;  water  16 

Sodium  sulphate  5;  dil.  sulphuric  acid  4 

Sodium  nitrate  3;  dil.  nitric  acid  2 

Ammonium  nitrate  1;  sodium  carbonate  1; 

water  1 

Sodium  sulphate  6;    ammonium  chloride  4; 

potassium  nitrate  2;  dil.  nitric  acid  4 

Sodium  phosphate  9;  dil.  nitric  acid  4 

Sodium  sulphate  6;  ammonium  nitrate  5; 

dil.  nitric  acid  4 


+32 

+32 
+32 
+32 
+32 

+50 
+50 

+50 
+50 
+50 

+50 

+50 
+50 

+50 


—12 

—25 
—40 

—  5 
—23 
—27 
—30 
—51 

+  4 
+  4 

+  4 
+  3 

—  3 

—  7 

—10 
—12 

—14 


72 

55 

59 
62 
83 

46 
46 

46 
47 
53 

57 

60 

62 

64 


TABLE  54. 
Properties  of  Saturated  Ammonia.t 


Pressure 

Vol.  of 

Vol.    of 

Wt.   of 

Temp. 

absolute 

Heat  of 

vapor 

liquid 

vapor 

deg.  F. 

Ibs.  per 

vaporization 

per  Ib. 

per  Ib. 

Ibs.  per 

sq.  in. 

CU.   ft.       j 

cu.  ft. 

cu.  ft. 

—40 

10.69 

579.67 

24.38 

.0234 

.0411 

—35 

12.31 

576.69 

21.21 

.0236 

.0471 

—30 

14.13 

573.69 

18.67 

.0237 

.0535 

—25 

16.17 

570.68 

16.42 

.0238 

.0609 

—20 

18.45 

567.67 

14.48 

.0240 

.0690 

—15 

20.99 

564.64 

12.81 

.0242 

.0775 

—10 

23.77 

561.61 

11.36 

.0243 

.0880 

—  5 

27.57 

558.56 

9.89 

.0244 

.1011 

±   0 

30.37 

555.50 

9.14 

.0246 

.1094 

+  5 

34.17 

552.43 

8.04 

.0247 

.1243 

+10 

38.55 

549.35 

7.20 

.0249 

.1381 

+20 

47.95 

543.15 

5.82 

.0252 

.1721 

+30 

59.41 

536.92 

4.73 

.0254 

.2111 

+40 

73.00 

530.63 

3.88 

.0257 

.2577 

+50 

88.96 

524.30 

3.21 

.02601 

.3115 

+60 

107.60 

517.93 

2.67 

.0265 

.3745 

+70 

129.21 

511.52 

2.24 

.0268 

.4664 

+80 

154.11 

504.66 

1.89 

.0272 

.5291 

+90 

182.80 

498.11 

1.61 

.0274 

.6211 

+100 

215.14 

491.50 

1.36 

.0279 

.7353 

*Tayler.    Pocket  Book  of  Refrigeration. 

t  Wood—  Thermodynamics,  Heat  Motors  and  Refrigerating  Machines. 

380 

TABLE  55. 

Solubility  of  Ammonia  in  Water  at  Different  Temperature* 
and  Pressures.      (Sims).* 

1  Ib.  of  water  (also  unit  volume)  absorbs  the  following 
quantities   of  ammonia. 


Absolute 

32° 

F. 

68°  I 

\ 

104° 

F. 

212° 

F. 

pressure 

in  Ibs. 

per 
sq.  in. 

LbS. 

Vols. 

LbS. 

Vols. 

LbS. 

Vols. 

Grms. 

Vols. 

14.67 

0.899 

1180 

0.518 

683 

0.338 

443 

0.074 

97 

15.44 

0.937 

1231 

0.535 

703 

0.349 

458 

0.078 

102 

16.41 

0.980 

1287 

0.556 

730 

0.363 

476 

0.083 

109 

17.37 

.029 

1351 

0.574 

754 

0.378 

496 

0.088 

115 

18.34 

.077 

1414 

0.594 

781 

0.391 

513 

0.092 

120 

19.30 

.126 

1478 

0.613 

805 

0.404 

•531 

0.096 

126 

20.27 

.177 

1546 

0.632 

830 

0.414 

543 

0.101 

132 

21.23 

.236 

1615 

0.651 

855 

0.425 

558 

0.106 

139 

22.19 

.283 

1685 

0.669 

878 

0.434 

570 

0.110 

140 

23.16 

.336 

1754 

0.685 

894 

0.445 

584 

0.115 

151 

24.13 

.388 

1823 

0.704 

924 

0.454 

596 

0.120 

157 

25.09 

.442 

1894 

0.722 

948 

0.463 

609 

0.125 

164 

26.06 

.496 

1965 

0.741 

973 

0.472 

619 

0.130 

170 

27.02 

.549 

2034 

0.761 

999 

0.479 

629 

0.135 

177 

27.99 

.603 

2105 

0.780 

1023 

0.486 

638 

28.95 

.656 

2175 

0.801 

1052 

0.493 

647 

30.88 

.758 

2309 

0.842 

1106 

0.511 

671 

32.81 

.861 

2444 

0.881 

1157 

0.530 

696 

34.74 

.966 

2582 

0.919 

1207 

0.547 

718 

36.67 

2.070 

2718 

0.955 

1254 

0.565 

742 

TABLE  56. 
Strength  of  Ammonia   Liquor.* 


Degrees 

Specific 

Percent- 

Degrees 

Specific 

Percent- 

Baume 

gravity 

age 

Baume 

gravity 

age 

10 

1.0000 

0.0 

20 

0.9333 

17.4 

11 

0.9929 

1.8 

21 

0.9271 

19.4 

12 

0.9859 

3.3 

22 

0.9210 

21.4 

13 

0.9790 

5.0 

23 

0.9150 

23.4 

14 

0.9722 

6.7 

24 

0.9090 

25.3 

15 

0.9655 

8.4 

25 

0.9032 

27.7 

16 

0.9589 

10.0 

26  (a) 

0.8974 

30.1 

17 

0.9523 

11.9 

27 

0.8917 

32.5 

18 

0.9459 

13.7 

28 

0.8860 

35.2 

19 

0.9396 

15.5 

29 

0.8805 

Note.— Sp.  gr.  of  pure  anhydrous  ammonia  =   .623 
(a)  Known  to  the  trade  as  "29^  per  cent." 
*Tayler.    Pocket-Book  of  Refrigeration. 

381 


TABLE  57. 
Properties    of    Saturated    Sulphur    Dioxide.       (Ledoux).* 


Temp,  of 
ebullition 
deg.  F. 

Absolute 
pressure 
Ibs.  per 
sq.  in. 
P  -^  144 

Total  heat 
from 
32  deg.  F. 

Latent  heat 
of  vapor- 
ization 

Heat  of 
liquid 
from 
32  deg.  F. 

Density  of 
vapor 
\vt.  per 
cu.  ft. 

—22 

5.56 

157.43 

176.99 

—19.06 

.076 

—13 

7.23 

158.64 

174.95 

—16.30 

.097 

—  4 

9.27 

159.84 

172.89 

-13.05 

.123 

5 

11.76 

161.03 

170.82 

—  9.79 

.153 

14 

14.74 

162.20 

168.73 

—  6.53 

.190 

23 

18.31 

163.36 

166.63 

—  3.27 

.232 

32 

22.53 

164.51 

164.51 

0.00 

.282 

41 

27.48 

165.05 

162.38 

3.27 

.340 

50 

33.25 

166.78 

160.23 

6.55 

.407 

59 

39.93 

167.90 

158.07 

9.83 

.483 

68 

47.61  • 

168.99 

155.89 

13.11 

.570 

77 

56.39 

170.09 

153.70 

16.39 

.669 

86 

66.36 

171.17 

151.49 

19.69 

.780 

95 

77.64 

172.24 

149.26 

22.98 

.906 

104 

90.31 

173.30 

147.02 

26.28 

1.046 

TABLE  58. 
Properties  of  Saturated  Carbon  Dioxide.f 


Temp,  of 

Absolute 

Total  heat 

Latent  heat 

Heat  of 

Density  of 

ebullition 
deg.  F. 

pressure 
in  Ibs. 
per  sq.  in. 

from 
32  deg.  F. 

of  vapor- 
ization 

liquid  from 
32  deg.  F. 

vapor  or 
wt.  per 
cu.  ft. 

—22 

210 

98.35 

136.15 

—37.80 

2.321 

—13 

249 

99.14 

131.65 

—32.51 

2.759 

—  4 

292 

99.88 

126.79 

—26.91 

3.265 

5 

342 

100.58 

121.50 

—20.92 

3.853 

14 

396 

101.21 

115.70 

—14.49 

4.535 

23 

457 

101.81 

109.37 

—  7.56 

5.331 

32 

525 

102.35 

102.35 

0.00 

6.265 

41 

599 

102.84 

94.52 

8.32 

7.374 

50 

680 

103.24 

85.64 

17.60 

8.  70S 

59 

768 

103.59 

75.37 

28.22 

10.356 

68 

864 

103.84 

62.98 

40.86 

12.480 

77 

968 

103.95 

46.89 

57.06 

15.475 

86 

1080 

103.72 

19.28 

84.44 

21.519 

•Kent's  M.  E.  Poclcet-Book. 
II.  C.  S.  Pamphlet  1238  B. 


382 


TABLE  59. 

Pressures   and  Boiling  Points   of    Liquids   Available   for  Ui 
in    Refrigerating    Machines.* 


Temperature 
of  ebullition 

Pressure  of  vapor 
Pounds  per  square  inch  absolute 

deg.  F. 

Sulphur 
dioxide 

Ammonia 

Carbon 
dioxide 

Pictet 
fluid 

—40 

10.22 

—31 

13.23 

—22 

5.56 

16.95 

—13 

7.23 

21.51 

251.6 

—  4 

9.27 

27.04 

292.9 

13.5 

5 

11.76 

33.67 

340.1 

16.2 

14 

14.75 

41.58 

393.4 

19.3 

23 

18.31 

50.91 

453.4 

22.9 

32 

22.53 

61.85 

520.4 

26.9 

41 

27.48 

74.55 

594.8 

31.2 

50 

33.26 

89.21 

676.9 

36.2 

59 

39.93 

105.99 

766.9 

41.7 

68 

47.62 

125.08 

864.9 

48.1 

77 

56.39 

146.64 

971.1 

55.6 

86 

66.37 

170.83 

1085.6 

64.1 

95 

77.64 

197.83 

1207.9 

73.2 

104 

90.  32* 

227.76 

1338.2 

82.9 

TABLE   60. 
Table  of  Calcium  Brine   Solution.f 


Deg. 
Baume 
60  deg. 

Per  cent, 
calcium 
by 
weight 

Lbs.  per 
cu.  ft. 
solution 

Specific 
gravity 

Specific 
heat 

Freezing 
point 
deg.    F. 

Amrn. 
gage 
pressure 

0 

0.000 

0.0 

.000 

1.000 

32.00 

47.31 

2 

1.886 

2.5 

.014 

.988 

30.33 

45.14 

4 

3.772 

5.0 

.028 

.972 

28.58 

43.00 

6 

5.658 

7.5 

.043 

.955 

27.05 

41.17 

8 

7.544 

10.0 

.058 

.936 

25.52 

39.35 

10 

9.430 

12.5 

.074 

.911 

22.80 

36.30 

12 

11.316 

15.0 

.090 

.890 

19.70 

32.93 

14 

13.202 

17.5 

.107 

.878 

16.61 

29.63 

16 

15.088 

20.0 

.124 

.866 

13.67 

27.04 

18 

16.974 

22.5 

.142 

.854 

10.00 

23.85 

20 

18.860 

25.0 

.160 

.844 

4.60 

19.43 

22 

20.746 

27.5 

.179 

.834 

—  1.40 

14.70 

24 

22.632 

30.0 

.198 

.817 

—  8.60 

9.96 

26 

24.518 

32.5 

.218 

.799 

—17.10 

5.22 

28 

26.404 

35.0 

.239 

.778 

—27.00 

.65 

30 

28.290 

37.5 

.261 

.757 

-39.20 

8.5*  vac. 

32 

30.176 

40.0 

.283 

—54.40 

15*     vac. 

34 

32.062 

42.5 

1.306 

—39.20 

4"     vac. 

"Kent's  M.  E.  Pocket-Book . 

tAm.  Sch.  of  Cor.  Dickerman-Boyer. 

383 


TABLE  61. 
Table  of  Salt  Brine  Solution.* 

(Sodium  chloride). 


Degrees 
Salom- 
eter  at 
60  deg.  F. 

Percent, 
by  wt. 
of  salt 

Pounds 
of  salt 
per  cu.  ft. 

Specific 
gravity 

Specific 
heat 

Freezing 
point 
deg.  F. 

Amm. 
gage 
pressure 

0 

0.00 

0.000 

1.0000 

1.000 

32.0 

47.32 

5 

1.25 

0.785 

1.0090 

.990 

30.3 

45.10 

10 

2.50 

1.586 

1.0181 

.980 

28.6 

43.03 

15 

3.75 

2.401 

1.0271 

.970 

26.9 

41.00 

20 

5.00 

3.239 

1.0362 

.960 

25.2 

38.96 

25 

6.25 

4.099 

1.0455 

.943 

23.6 

37.19 

30 

7.50 

4.967 

1.0547 

.926 

22.0 

33.44 

35 

8.75 

5.834 

1.0640 

.909 

20.4 

33.69 

40 

10.00 

6.709 

1.0733 

.892 

18.7 

31.93 

45 

11.25 

7.622 

1.0828 

.883 

17.1 

£0.88 

50 

12.50 

8.542 

1.0923 

.874 

15.5 

28.73 

65 

13.75 

9.462 

1.1018 

.864 

13.9 

27.24 

60 

15.00 

10.389 

1.1114 

.855 

12.2 

25.76 

65 

16.25 

11.384 

1.1213 

.848 

10.7 

24.46 

70 

17.50 

12.387 

1.1312 

.8-12 

9.2 

23.16 

75 

18.75 

13.396 

1.1411 

.835 

7.7 

21.82 

80 

20.00 

14.421 

1.1511 

.829 

6.1 

20.43 

85 

21.25 

15.461 

1.1614 

.818 

4.6 

19.16 

90 

22.50 

16.508 

1.1717 

.806, 

3.1 

18.20 

95 

23.75 

17.555 

1.1820 

.795 

1.6 

16.88 

100 

25.00 

18.610 

1.1923 

.783 

0.0 

15.67 

TABLE  62. 

Horse-Power  Required  to  Produce  One  Ton  of  Refrigeration.! 

Condenser  pressure  and  temperature. 


P 

103 

115 

127 

139 

153 

168 

184 

200 

218 

§p 

T 

65 

70 

75 

80 

85 

90 

95 

100 

105 

*i 

&  9 

s  13 

P.16 

h  20 
224 
228 

S33 

'S  39 

—20° 
—15 
—10 
—  5 
0 
5 
10 
15 
20 
25 

1.0584 
.9972 
.9026 
.8184 
.7352 
.6665 
.5915 
.5410 
.4745 
4103 

1.1304 
1.0694 
.9777 
.8833 
.8008 
.7312 
.6629 
.5998 
.5340 
.4659 

1.2051 
1.1450 
1.0453 
.9537 
.8648 
.7946 
.7257 
.6641 
.5923 
.5227 

1.2832 
1.2221 
1.1183 
1.0230 
.9328 
'.8593 
.7894 
.7276 
.6716 
.5804 

1.3611 
1.3001 
1.1926 
1.0935 
1.0019 
.9278 
.8545 
.7924 
.7148 
.5992 

1.4427 
1.4101 
1.2602 
1.1679 
1.0718 
.9978 
.9205 
.8553 
.7796 
7022 

1.5251 
1.4609 
1.3471 
1.2437 
1.1467 
1.0656 
.9911 
.9224 
.8420 
.7667 

1.6090 
1.5458 
.4352 
.3209 
.2194 
.1381 
.0595 
.9943 
.9031 
.8283 

1.6910 
1.6300 
.5033 
.3961 
.2547 
.2121 
.1294 
.0603 
.9736 
.8922 

"3  45 
«61 

30 
35 

.3509 
.3005 

.4056 
.3546 

.4612 
.4101 

.5178 
.4666 

.5755 
.5214 

.6353 
.5804 

.6944 
.6398 

.7500 
.7003 

.8172 
.7629 

Note.— The  above  figures  are  purely  theoretical. 
50  per  cent,  must  be  added. 

*Am.  Sch.  of  Cor.  Dickerman-Boyer. 
tDe  La  Vergne  Catalog. 

384 


In  practice  about 


TABLE  63. 

Cubic  Feet  of  Ammonia  Gas  per  Minute  to  Produce  One  Ton 
of  Refrigeration  per  Day.* 

Condenser  pressure  and  temperature. 


1 

Press. 

103 

115 

127 

139 

153 

168 

185 

200 

218 

105° 

Press. 

Temp. 

65° 

70° 

75° 

80° 

85° 

90° 

95° 

100° 

2 

4 

—20° 

5.84 

5.90 

5.96 

6.03 

6.06 

6.16 

6.23 

6.30 

6.43 

f£ 

6 

—15° 

5.35 

5.40 

5.46 

5.52 

5.58 

5.64 

5.70 

5.77 

5.83 

CJ  .2 

9 

—10° 

4.66 

4.73 

4.76 

4.81 

4.86 

4.91 

4.97 

5.05 

5.08 

13 

fro 

4.09 

4.12 

4.17 

4.21 

4.25 

4.30 

4.35 

4.40 

4.44 

»->  s 

16 

0° 

3.59 

3.63 

3.66 

3.70 

3.74 

3.78 

3.83 

3.87 

3.91 

II 

20 

5° 

3.20 

3.24 

3.27 

3.30 

3.34 

3.38 

3.41 

3.45 

3.49 

«£ 

24 

10° 

2.87 

2.90 

2.93 

2.96 

2.99 

3.02 

3.06 

3.09 

3.12 

£" 

28 

15° 

2.59 

2.61 

2.65 

2.68 

2.71 

2.73 

2.76 

2.80 

2.82 

be 

33 

20° 

2.31 

2.34 

2.36 

2.38 

2.41 

2.44 

2.46 

2.49 

2.51 

<M 

39 

25° 

2.06 

2.08 

2.10 

2.12 

2.15 

2.17 

2.20 

2.22 

2.24 

K 

45 

30° 

1.85 

1.87 

1.89 

1.91 

1.93 

1.95 

1.97 

2.00 

2.01 

51 

35° 

1.70 

1.72 

1.74 

1.76 

1.77 

1.79 

1.81 

1.83 

1.85 

TABLE   64. 
Table   of  Refrigerating   Capacities.! 


Size  of  building 


Number  of  eu.  ft.  per  ton  of  refrigera- 
tion at  temperatures  given 


Dimen- 

Con- 

Sur- 

Ratio 

Temperatures 

sions  of 

tents 

face 

cu.  ft 

building 

cu.  ft 

in  sq. 
A*. 

to  sq. 

it. 

ft. 

0° 

8° 

16° 

24° 

32° 

40° 

48° 

5x4x5 

100 

130 

1.3 

900 

1100 

1300 

1500 

1700 

1900 

2100 

8x10x10 

800 

520 

.65 

1800 

2200 

2600 

3000 

3400 

3800 

4200 

25x40x10 

10000 

3300 

.33 

3600 

4400 

5200 

6000 

6700 

7600 

8400 

20x50x20 

20000 

4800 

.24 

4860 

5940 

7020 

8100 

9180 

10260 

11340 

40x50x20 

40000 

7600 

.19 

6300 

7700 

9100 

10500 

11900 

13300 

14700 

60x50x20 

60000 

10400 

.17 

6840 

8360 

9880 

11400 

12920 

14440 

15960 

80x50x20 

80000 

13200 

.165 

7200 

8800 

10700 

12000 

13600 

15200 

16800 

100x50x20 

100000 

16000 

.16 

7200 

8800 

10400 

12000 

13600 

15200 

16800 

100x100x20 

200000 

28000 

.14 

8100 

9900 

11700 

13000 

15300 

17100 

18900 

100x100x40 

400000 

36000 

.09 

13050 

15950 

18850 

21750 

24650 

27550 

30450 

100x100x60. 

600000 

44000 

.073 

16200 

19800 

23400 

27000 

30600 

34200 

37800 

100x100x80 

800000 

52000 

.065 

18000 

22000 

26000 

30000 

34000 

38000 

42000 

100x100x100 

1000000 

60000 

.06 

19350 

23650 

27950 

32250 

36550 

40850 

45150 

*Featherstone  Foundry  and  Machine  Co.  Catalog. 
tTayler.    P.  B.  of  R. 


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Table   66. 

Temperatures  to  Which  Ammonia  Gas  Is  Raised  by 
Compression.* 


Tempera- 
ture of 
suction 

Absolute 
condensing 
pressure 

Absolute  suction  pressure 

20 

25 

30 

35 

40 

45 

Odeg.  F. 

90 

199 

165 

138 

116 

98 

83 

110 

232 

196 

166 

145 

126 

109 

130 

261 

222 

193 

169 

150 

132 

150 

285 

246 

216 

191 

171 

153 

160 

296 

257 

226 

202 

181 

163 

5  deg.  F. 

90 

266 

172 

145 

123 

104 

89 

110 

239 

203 

174 

151 

132 

115 

130 

268 

230 

200 

176 

156 

139 

150 

293 

254 

223 

198 

178 

160 

160 

305 

265 

234 

209 

188 

170 

10  deg.  F. 

90 

213 

178 

151 

129 

110 

96 

110 

247 

210 

181 

158 

139 

122 

130 

275 

237 

207 

183 

163 

145 

150 

301 

262 

231 

205 

185 

167 

160 

313 

273 

241 

216 

195 

176 

15  deg.  F. 

90 

221 

185 

158 

135 

117 

101 

110 

254 

217 

188 

164 

145 

128 

130 

283 

245- 

214 

191 

170 

152 

150 

309 

269 

238 

213 

192 

173 

160 

321 

281 

249 

223 

202 

183 

20  deg.  F. 

90 

228 

192 

164 

141 

123 

106 

110 

262 

224 

195 

171 

150 

134 

130 

291 

252 

222 

197 

176 

158 

150 

317 

277 

245 

220 

198 

180 

160 

329 

288 

256 

230 

209 

190 

25  deg.  F. 

90 

235 

199 

171 

148 

129 

111 

110 

269 

230 

200 

178 

155 

140 

130 

299 

259 

229 

204 

183 

165 

150 

325 

284 

253 

227 

205 

187 

160 

338 

296 

264 

237 

216 

197 

30  deg.  F. 

90 

242 

206 

177 

154 

134 

118 

110 

277 

239 

208 

184 

164 

147 

130 

307 

267 

236 

211 

190 

171 

150 

334 

292 

260 

234 

•212 

193 

160 

346 

304 

271 

245 

223 

203 

35  deg.  F. 

90 

249 

213 

182 

160 

141 

124 

110 

286 

246 

215 

191 

170 

153 

130 

315 

274 

243 

217 

196 

178 

150 

341 

300 

268 

241 

219 

200 

160 

354 

312 

279 

252 

230 

210 

*Tayler.    P.  B.  of  R. 


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TABLE   68. 
Time  Required  to  Freeze  Ice  in  Cells  or  Cans,  (a)   (Slebert).* 


Temp, 
deg.  F. 

Thickness  in  inches 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

10 
12 
14 
16 

18 
20 
22 
24 

0.32 
0.35 
0  39 

1.28 
1.40 
1  56 

2.86 
3.15 
3  50 

5.10 
5.60 
6  22 

8.00 
8.75 
9  70 

11.5 
12.6 
14  0 

15.6 
17.3 
19.0 

20.4 
22.4 
25.0 

25.8 
28.4 
31.5 

31.8 
35.0 
39.0 

38.5 
42.3 

47.0 

45.8 
50.4 
56.0 

0.44 
0.50 
0.58 
0.70 
0.88 

1.75 
2.00 
2.32 
9.80 
3.50 

3.94 

4.50 
5.25 
6.30 
7.86 

7.00 
8.00 
9.30 
11.20 
14.00 

11.00 
12.50 
14.60 
17.50 
21.00 

15.8 
18.0 
21.0 
25.2 
31.5 

21.5 
24.5 

28.5 
34.3 
42.8 

28.0 
32.0 
37.3 
44.8 
56.0 

35.5 
40.5 
47.2 
56.7 
71.0 

43.7 
50.0 
58.3 
70.0 

87.5 

53.0 
60.5 

70.5 
84.7 
106.0 

63.0 
72.0 
84.0 
ICO.O 
126.0 

(a)  Time  required  from  one  wall,  for  plate  ice,  two  times  the  above  values. 

TABLE   69. 
Standard    Sizes   of   Ice   Cans.f 


Size  of 
cake,  in 
pounds 

Size  of 
top, 
inches 

Size  of 
bottom, 
inches 

Inside 
depth, 
inches 

Outside 
depth, 
inches 

Size  of 
band, 
inches 

50 
100 
200 
300 
400 

8x8 
8x16 
Iiy2x22y2 
Il%x22i£ 
11^x221/2 

7^x7^ 
7*4x15^4 
101,2x211/2 

ioy2x2iy2 

10y2x21^ 

31 
31 

31 
44 
57 

32 

32 
32 

45 
58 

%xiy2 

y4xiya 

%x2 

y4x2 
y*x2 

TABLE  70. 
Cold    Storage    Temperatures    for    Various    Articles.* 


Article 

Temp, 
deg. 
F. 

Article 

Temp, 
deg. 
F. 

Article 

Temp, 
deg. 

Apples 

32-36 

Fruits  

26-55 

Oranges 

45-50 

Asparagus 

34 

Fruits    (dried).. 

35-40 

Oysters        ._  — 

33-35 

Bananas  _      

40-45 

Fruits    (canned) 

35 

Oysters  (in 

Beans  (dried) 

32-40 

Furs  (un- 

tubs) 

25 

Berries  (fresh).. 
Buckwheat 

36-40 

dressed)    
Furs  (dressed)  _ 

35 
25-32 

Oysters  (in 
shells) 

33 

flour      

40 

Game  (frozen).. 

25-28 

Peaches 

45-55 

Butter          _    __ 

32-38 

Game  (to 

Pears      _    

34-36 

Cabbage 

34 

freeze) 

15-28 

Peas  (dried) 

40 

Cantaloupes 

40 

Grapes      

36-38 

Pork 

34 

Celery 

32-34 

Hams 

30-35 

Potatoes 

36-40 

Cheese 

32-33 

Hops 

33-40 

Poultry 

Chocolate 

40 

Honey          

45 

(frozen) 

28-30 

Cider 

30-40 

Lard    .    

34-45 

Poultry  (to 

Claret 

45-50 

Lemons 

36-40 

freeze) 

18-22 

Corn  (dried)  
Cranberries 

35 

34-36 

Meat  (canned).. 
Meat  (fresh)  

35 
34 

Sugar,  etc.   
Syrup 

40-45 
35 

Cream      _ 

35 

Meat  (frozen)    _ 

25-28 

Tobacco 

35 

Cucumbers 

39 

Milk 

32 

Tomatoes 

36 

Dates 

55 

Nuts 

35 

Vegetables 

34-40 

Eggs 

33-35 

Oat  meal  

40 

Watermelons 

34 

Figs 

55 

Oil  

35 

Wheat  flour 

40 

Fish  (fresh)    _.. 

25-30 

Oleomargarine  _ 

35 

Wines  

40-45 

Fish  (dried)  ... 

35 

Onions  

34-40 

Woollens,  etc... 

25-32 

*Tayler.    P.  B.  of  R. 
tAs  adopted  by  the  Ice  Machine  Builders'  Association  of  the  U.  S. 
389 


APPENDIX  III 


391 


Tests  of  House  Heating  Boilers. 

The  following  extract  from  a  series  of  tests  on  a  Num- 
ber S-48-7  Ideal  Sectional  Boiler  from  the  reports  of  the 
American  Radiator  Company's  Institute  of  Thermal  Re- 
search, Buffalo,  New  York,  will  be  of  interest. 

Size  of  grate 48x64%  in.       Grate  area 21.6  sq.  ft. 

Heating  surface— total 300.0  sq.  ft. 

Hard      Hard      Hard 

0— Fuel  used  in  tests Coal       Coal       Coal 

1— No.   of  boiler _ S-48-7      S-48-7      S-48-7 

2— Duration  of  test  hours 8:00        7:00        8:00 

4— Fuel  burned  during  test,  Ibs 1360.00    1344.00    1434.00 

5— Fuel  per  hour,  Ibs.  170.00     192.00     178.20 

6— Fuel  per  sq.  ft.  grate  per  hour,  Ibs 7.90         8.95         8.35 

7— Stack  temperature,  degrees  Fahrenheit 750.00     725.00     600.00 

8— Evaporation  per  sq.  ft.  of  heating  surface 

per  hour,  Ibs. 4.97         5.60         5.24 

9 — Evaporative  power  available — Ibs.  of  water 

per  Ib.  of  coal 8.80        8.75        8.77 

10— Boiler-power  (evaporation  per  hour)— Ibs. 

(item  5  x  item  9) 1496.00    1680.00    1562.00 

11— Capacity— sq.  ft.   (item  10  -f-  0.22) 6800.00    7640.00    7100.00 

12— Capacity— sq.  ft.  (item  10  -5-  0.25) 5980.00    6720.00    6250.00 

Catalog  rating : 5700  sq.   ft. 

The  accompanying  figure  shows  the  combustion  chart 
as  developed  for  this  same  boiler.  The  tests  were  run  to 
find  the  evaporative  power  and  ca- 
pacity with  varying  amounts  of 
coal  burned  per  hour.  Coal  was 
fired  at  regular  intervals  and  the 
steam  pressure  was  maintained  at 
two  pounds  gage  on  the  radiation. 
Line  11  gives  the  capacity  in 
square  feet  of  radiation  including 
mains  and  risers,  at  the  rate  of 
.22  pound  of  steam  per  square 
foot  per  hour.  Line  12  gives  the 
capacity  at  .25  pound  of  steam  per 
square  foot  per  hour.  In  average 
service  about  one-third  of  these 

quantities  of  coal  would  be  burned.  The  catalog  rating  is 
based  upon  burning  167.5  pounds  of  coal  per  hour  and  an 
evaporation  of  8.5  pounds  of  water  per  pound  of  coal  (rates 
of  combustion  and  evaporation  that  seem  justifiable).  As 


1600 
1500 

o, 


7C/ 


•487 


392 


will  be  seen  from  lines  5  and  9  the  actual  amount  of  coal 
burned  and  the  actual  evaporation  in  each  test  exceed  this 
figure.  Multiplying-  167.5  by  the  assumed  evaporative  rate 
of  8.5  and  dividing  by  .25  =  5700  square  feet.  Comparing 
with  column  2,  line  5  times  line  9  divided  by  .25  gives  6720 
square  feet,  which  is  above  'the  catalog  rating.  Test  number 
two  compared  With  test  num'ber  one  shows  that  by  in- 
creasing the  amount  of  coal  from  170  pounds  to  192  pounds 
per  hour  increases  the  boiler  capacity  740  square  feet. 


39* 


Data    Required    for    Estimating    Plain    Hot    Water    or    Steam 
Plants. 


Name 
of 
room 

K  0 

V  = 

1= 

Size  of 
room 

Cubic  contents 

I 

"tii 
& 
6 

£ 

C3 
£ 

1 

cr 
GO 

Radiators 
Steam  or  water 

Remarks: 
Cold  floor, 
ceiling,  etc. 

be 
S 

® 
2 

£ 

jet 

".i. 

B 

£ 

Direct 
indirect 

Indirect 

Number 

f 

CO 

§ 

B 

1 

Date 191_._ 

Owner  of  building Address 

Architect  Address 

Kind  of  building Location 

Nearest  freight  station 

Temperature  in  living  rooms Kind  of  fuel  used 

Height  of  cellar Size  of  smoke  flue x 


Items  to  Estimate  on. 

Boiler  and  foundation 

Smoke  pipe  and  damper 

Thermometers  and  pressure  and  safety  gages 

Draft  regulation 

Firing  tools 

Filling  and  blow-off  connection 

Pipe  and  fittings 

Sq.  ft.  of  radiation 

Cut-off  valves  and  radiator  valves 

Air  valves 

Radiator  wall  shields 

Temperature  control 

Humidifying  apparatus  

Floor  and  ceiling  plates 

Hangers  

Expansion  tank 

Cold  air  ducts,  stack  boxes  and  registers _ 

Pipe  covering  _ 

Bronzing   

Labor  of  installation 

Freight' and  cartage 

Per  cent,  of  profit 

Total  bid 

Submitted  by 


394 


INDEX 


Absolute  pressure,  12 
temperature,  12 

Absorbers,  300 

Absorption  system  of  refrigeration, 

294 
and  compression  system  compared, 

302 

system  condensers  for,  299 
system,  elevation  of,  296 
system  pumps  for,  301 

Accelerated  systems  hot  water,  95 

Adaptation  of  district  steam  to  pri- 
vate plants,  267 

Advantages  of  vacuum  systems,  142 

Air,  amount  to  burn  carbon,  35 
circulation  furnace  system,  53 
circulation  within  room,  76 
composition,  16 
duct,  fresh,  59 

exhausted,  actual  from  nozzle,  188 
exhausted  per  hour  plenum  system, 

'170 

h.  p.  in  moving,  192 
h.  p.  in  moving,  table,  186 
humidity  of,  25 
leakage,  heat  loss  by,  43 
moisture  required  by,  30 
needed  plenum  system,  172 
per  person,  table,  24 
required  as  heat  carrier,  54 
temperature  at  register,  56 
valves,  112 

velocities  of  in  convection,  31 
velocities,  measurement  of,  32 
velocities,  plenum  system,  table, 

172,  184 

required,  ventilating  purposes,  21 
washing  and  humidifying,  167 

Ammonia  for  one- ton  refrig.,  385 
solubility  in  water,  381 
strength  of  liquor,  381 

Anchors,  types  of,  221 

Anemometer,  32 

Appendix 

table    1  squares,  cubes,  etc.,  328 
table    2  trigonometric    functions, 

334 

table    3  equivalents  of  units,  334 
table    4  properties  of  steam,  335 
table    5  Naperian  logarithms,  338 
table    6  water  conversion  factors, 

338 
table    7  volume  and  wt.  of  dry  air, 

339 

table    8  weight  of  pure  water,  340 
table    9  boiling    points    of    water, 

342 
table  10  weight  of  water  in  air,  342 


table  11  relative  humidities,  343 


table  12  properties  of  air,  344 
table  13  dew  points  of  air,  345 
table  14  fuel  values  Am.  coals,  348 
table  15  cap.  of  chimneys,  349 
table  16  equalization  of  smoke 

flues,  350 

table  17  dimensions  of  reg.,  350 
tables  18,  20  cap.  of  fur.,  351,  352 
table  19  cap.  pipes  and  reg.,  351 
table  21  area  vertical  flues,  352 
table  22  sheet  metal  dim.,  353 
table  23  weight  of  G.  I.  pipe,  354 
table  24  sp.  ht.,  etc.,  of  substances, 

355 

tables  25,  26  water  pressures,  356 
table  27  wrought  iron  pipes,  357 
table  28  expansion  of  pipes,  358 
table  29  tapping  list  of  rad.,  358 
table  30  pipe  equalization,  359 
table  31  cap.  hot  water  risers,  360 
table  32  cap.  steam  pipes,  360 
table  33  cap.  hot  water  pipes,  361 
table  34  cap.  hot  water  mains,  361 
tables  35,  36  sizes  of  steam  mains, 

362,  363 

table  37  friction  in  pipes,  364 
table  38  grav.  and  vac.  returns,  365 
table  39  expansion  tanks,  365 
table  40  sizes  of  flanged  fittings, 

366 

table  41  pipe  fittings,  366 
table  42  friction  in  air  pipes,  367 
table  43  temp,  for  testing  steam 

plants,  370 

table  44  spec,  for  boilers,  371 
table  45  heat  trans,    through  pipe 

covering,  372 

table  46  factors  of  evap.,  373 
table  47  heat  in  feed  water,  373 
table  48  sizes  of  Vento  heater,  374 
table  49  steam  used  by  engines,  375 
tables  50,  51,  52  speeds,  cap.   and 

h.  p.  of  various  fans,  376, 

378 

table  53  freezing  mixtures,  380 
table  54  properties  of   ammonia, 

380 
table  55  sol.  of  ammonia  in  water, 

381 
table  56  strength  of  ammonia 

liquor,  381 
table  57  prop,   of  sulphur  dioxide, 

382 
table  58  prop,  of  carbon  dioxide, 

382 

table  59  boiling  pts.  of  liquids,  383 
table  60  calcium  brine  sol.,  383 
table  61  salt  brine  sol.,  384 
table  62  horse-power  for  refrig.,  384 


395 


396 


INDEX 


table  63  ammonia  for  one-ton 

refrig.,  385 

table  64  refrigeration  caps.,  385 
table  65  cost  of  ice  making,  386 
table  66  temperature  of  ammonia, 

387 

table  67  hydrometer  scales,  388 
table  68  time  to  freeze  ice,  389 
table  69  sizes  of  ice  cans,  389 
table  70  temp,  for  cold  storage,  389 

Application  of  formula  in  furnace 

heating,  62 
of  plenum  system,  200 

Area  of  ducts,  plenum  system,  172 
of  chimney  determination  of,  35 
of  grate,  59 

Arrangement  of  Vento  heaters,  161 
of  coils,  plenum  system,  160 

Automatic  vacuum  system,  149 
valves,  149 

Basement  plans  plenum  system,  203 
Belvac  thermofiers,  148 
Blowers  and  fans,  speeds  of,  table, 
197 

work,  Carpenter's  rules,  194 
Boilers,  251 

feed  pumps,  249 

capacity  and  number  of,  255 

radiation  supplied  by,  252 

plant  capacity  of,  255 

steam,  108 

tests  of,  392 

Boiling  point  of  water,  table,  342 
Boiling  points  of  liquids,  383 
Brine  cooling  system,  cap.  of,  315 
British  thermal  unit,  10 
B.  t.  u.  lost  in  plenum  system,  176 
Building  materials,  conductivities  of, 
40 

Calcium  brine  solution,  383 
Calculating  chimney  areas,  35    . 

heat  loss,  45-46 
Calorie,  10 
Carbon  amount  of  air  to  burn,  35 

dioxide,  18 

dioxide  per  cent.,  table,  19 

dioxide  tests  for,  19 
Carpenter's  practical  rules,  194 
Cast  radiators,  103 

surfaces,  plenum  system,  161 
Centrifugal  pumps,  247 
Check  valve,  111 

Chimney  area,  determination  of,  35 
Chimneys,  36 

capacity  of,  table,  349 
Circulating  system  for  refrigerating, 
302 

duct  in  furnace  design,  72 

water  to  condense  steam,  237 
Classification  of  radiators,  104 
Coal,  fuel  values  of,  table,  348 
Coils,  arrangement  of  in  pipe  heater, 
180 


arrangement  of  Vento  in  stacks, 
182 

heat  transmission  through,  174 

heat  transmission  through  Vento, 
table,  177 

sq.  ft.  for  cooling,  311 

surface,  plenum  system,  173 

temp,  leaving  Vento,  table,  180 
Cold  air  system  of  refrigeration,  2S4 
Combination  systems,  110 

heaters,  70 
Comparison    of    furnace    and    other 

systems,  51 

Composition  of  air,  16 
Compression  and  absorption  system 
compared,  302 

systems,  condensers  for,  289 

system  of  refrigeration,  286 
Condensation,  dripping  from  mains, 
267 

return  to  boilers,  133 
Condenser,  concentric  tube,  289 

enclosed,  290 

for  compression  systems,  289 

submerged,  290 

for  exhaust  steam,  238 

heating  surface  in,  239 
Conduction,  14 

of  building  material,  table  of,  40 
Conduits,  district  heating,  212 
Convection,  15 

Conversion  factors  for  water,  338 
Coolers  for  weak  liquor,  301 
Cost    of   heating   from  central  sta- 
tion, 258 

of  ice  making,  316,  386 

Data  for  estimate,  394 
Data,  table  for  plenum  system,  202 
Design,  hot  water  and  steam,  114 
Determination  of  pipe  sizes,  121 
Dew  point,  influence  of  on  refrigera- 
tion, 305 

Dew  points  of  air,  345 
Direct  radiation,  tapping  list,  table, 

358 

Dirt  strainer,  Webster,  147 
District  heating 

adaptation  to  private  plants,  267 

amount  of  radiation  supplied  by 
one  horse-power  exhaust  steam, 
237 

amount  of  radiation  supplied,  237 

amount  of  radiation  supplied  by 
reheater,  241 

application  to  typical  design,  268 

boiler  feed  pumps,  249 

boilers,  251 

by  steam,  264 

capacity  of  boiler  plant,  255 

centrifugal  pumps,  247 

circulating  pumps,  244 

city  water  supply,  249 

classification.  229 
condensation  from  mains,  267 


INDEX 


397 


conduits,  212 

cost  of  heating,  258 

cost,  summary  of  tests,  260 

design  for  consideration,  222 

dripping  condensation  from  mains, 

267 

diameter  of  mains,  265 
economizer,  253 
exhaust  steam  available,  223 
future  increase,  231 
general  application  of  design,  268 
heat    available   in  exhaust    steam, 

225 

heating  by  steam,  264 
heating  surface  in  reheater,  239 
high  pressure  steam  heater,  244 
hot  water  systems,  229 
important  reheater  details,  242 
layout  for  conduit  mains,  218 
power  plant  layout,  259 
pressure  drop  in  mains,  231,  265 
radiation  in  district,  231 
radiation  supplied  by  1  h.  p.  of  ex. 

St.,  237 
radiation  supplied  by  economizer, 

253 
radiation  supplied  per  boiler  h.  p., 

252 

references  on  district  heating,  270 
regulation,  263 
reheater  details,  242 
reheater  for  circulating  water,  238 
reheater  tube  surface,  241 
scope  of  work,  209 
service  connections,  235 
steam  available  for  heating,  236 
systems  classified,  229 
typical  design,  222 
velocity  of  water  in  mains,  234 
water  per  hour,  as  heating  medium, 

230 

water  to   condense  one  pound   of 
'  steam,  237 

Division  of  coils,  plenum  sys.,  162 
Ducts,  furnace,  cold  air,  59 
plenum  system,  165-166 
recirculating,  72 

Economizers,  253 

radiation  supplied  by,  253 

surface,  255 

Efficiency  of  plenum  coils,  table,  175 
Electrical  heating,  279 

formulas  used  in,  279 

future  of,  282 

references,  282 
Electric  pumps,  137 
Engine,  size  of,  197 
Equivalents  of  units,  334 
Evaporators  for  refrig.,  292 
Exchangers,  301 
Exhaust  steam  available  in  district 

plants,  223 
Exhaust  steam  condenser,  238 


Expansion  joints,  218 

tanks,  113,  365 
Exposure  heat  losses,  table,  43 

Factors  of  evaporation,  373 
Factor  table,  velocity  and  vol.,  188 
Fans  and  blowers,  155 

drives,  195 

housings,  157 

power  of  engine  for,  197 

size  of  parts,  195 

speed  of,  196 

Fire  places,  stoves,  etc.,  153 
Fittings,  steam  and  hot  water,  110, 

366 
Floor  plans  for  furnace  heating, 

64-66 

Floor  plans  for  plenum  sys.,  203-205 
Formulas,  empirical  for  radiation, 

117 

Freezing  mixtures,  380 
Fresh  air  duct,  59-71 
Fresh  air  entrance  to  bldgs.,  159 
Friction  diagrams,  368,  369 

in  pipes,  364 

of  air  in  pipes,  367 
Fuel  values  of  Am.  coals,  table,  348 
Furnace, 

air  circulation  within  room,  76 

foundations,  71 

heating,  51 

location,  71 

selection,  67 
Furnace  system,  air  circulation,  53 

air  required  as  heat  carrier,  54 

circulating  duct  in,  72 

design  of,  62 

essentials  of,  52 

fan  in,  77 

fresh  air  duct  in,  71 

grate  area  in,  59 

gross  register  area  in,  57 

heat  stacks,  sizes  of,  57 

heating  surface  in,  61 

leader  pipes  in,  59,  73 

net  vent  register  in,  56 

plans  for,  64 

points  to  be  calculated  in,  53 

registers,  temperatures  in,  56 

stacks  or  risers  in,  74 

three  methods  of  installation,  55 

vent  stacks,  76 

Gage  pressure,  12 

Gallon  degree  calculation,  315 

Gate  valve,  111 

Generators,  298 

Globe  valve,  111 

Grate  area,  boilers  and  heaters,  123 

Grate  area  for  furnaces,  59 

Greenhouse  heating,  118 

Gross  register  area,  51 

Hammer,  water,  133 


398 


INDEX 


Heat  given  off  by  persons,  lights, 
etc.,  49 

latent,  13 

measurement  of,  10 

mechanical  equivalent  of,  13 

stacks,  sizes  of,  57,  74 
Heaters,  hot  water,  108 
Heating,  district,  cost  of,  258 
Heating  surface  in  coils,  plenum  sys- 
tem, 159 

Heating  sur.,  in  economizer,  254 

in  furnace  system,  61 

in  reheater,  239 

per  h.  p.  in  reheater,  241 
Heat  loss,  43,  44,  45,  46 

calculation  of,  45 

calculation  for  refrig.,  308 

chart,  81 

combined,  47 

for  a  10  room  house,  table,  63 
High  pressure  heater,  244 
High  pressure  steam  trap,  134 
Horse-power,  in  moving  air,  192 

of  engine  for  fan,  197 

required  to  move  air  in  plenum  sys- 
tem, 193 
Hot  air  pipes,  cap.  of,  table,  351 

water  heaters,  108 

water  pipes,  capacity  of,  table,  361 

water  radiators,  106 

water  risers,  cap.  of,  table,  360 

water  system,  85 

water  used  in  indirect  coils  in  ple- 
num system,  183 
Hot  water  and  steam  heating, 

accelerated  systems,  95 

calculation  of  rad.  sur.  for,  114 

classifications,  87 

connection  to  radiators,  124 

determination  of  pipe  sizes,  121 

diagrams  for,  91 

empirical  formula  for,  117 

expansion  tank  for,  113 

for  district  heating,  229 

fittings,  110 

grate  area  for  heaters,  123 

greenhouse  radiation,  118 

layout,  128 

location  of  radiators  for,  124 

parts  of,  85 

pitch  of  mains  for,  124 

principles  of  design  of,  114 

second  classification  of,  88 

suggestions  for  operating,  137 

temperature,  table,  120 
Humidity  of  the  air,  25 
Humidities,  relative,  table,  343 
Hydrometric  scales,  388 
Hygrodeik,  27 
Hygrometer,  26 
Hygrometric  chart,  29 

Ice  making, 

capacity,  calculation,  314 
costs  of,  316 


Indirect  radiators,  88 

Insulation  of  steam  pipes,  131,  309 

'K'  values  for  pipe  coils,  table,  174 
'K'  values  for  Vento  coils,  177 

Latent  heat,  13 

Layout  for  furnace  system,  64 

for  hot  water  heating  plant,  128 

for  plenum  system,  163 

of  power  plant,  259 

main  and  riser,  131 

steam  mains  and  conduits,  218 
Leader  pipes,  58 
Location  of  furnaces,  71 

of  radiators,  124 
Low  pressure  steam  traps,  133 

Main  and  riser  layout,  131 
Mains,  cap.  of  hot  water,  table,  361 

condensation,  dripping  from,  267 

diameter  of,  234 

pitch  of,  124 

pressure  drop  and  diam.  of,  265 

velocity  of  water  in,  234 
Manholes,  222 
Measurement  of  air  velocities,  32 

of  heat,  10 

of  high  temperatures,  11 
Mechanical  equivalent  of  heat,  13 
Mechanical  vacuum  steam  htg.  sys., 

advantages  of,  142 

automatic  pump  for,  144 

automatic  system,  149 

Dunham  system,  150 

Paul  system,  150 

principal  features  of,  143 

Van  Auken,  148 

Webster  system,  145 
Mechanical    warm    air    heating    and 
ventilating  sys.,  153,  169,  184 

blowers  and  fans  for,  155 

definitions  of  terms,  169 

elements  of,  153 

exhaust,  154 

heat  loss  and  cu.  ft.  air  exhausted, 
170 

theoretical  considerations  for,  169 

variations  in  design  of,  154 
Mills  system  (attic  main),  90,  93 
Modulation  valve  for   Webster  sys- 
tem, 147 
Moisture,  addition  of,  to  air,  30 

with  air,  25 

Naperian  logarithms,  table,  338 
Nitrogen,  17 
'n,'  values  of,  47 

Operation  of  furnaces,  78 

of   hot   water   heaters   and   steam 
boilers,  137 

suggestions  for,  137 
Outside  temp,  for  design,  79 
Oxygen,  17 


INDEX 


399 


Packless  valves,  112 
Paul  sys.  of  mech.  vac.  heating,  150 
typical  piping  connections  for,  150 
Pipe  coil  radiators,  104 
capacity   of,   in   sq.    ft.   of   steam 

radiation,  360 
equalization,  table  of,  359 
for  refrigeration,  294 
line  refrigeration,  306 
sizes,  determination  of,  121 
Pipe,  leader,  58 
Piping  connection  around  heater  and 

engine,  200 

connections  for  auto.  vac.  sys.,  149 
connections  for  Paul  sys.,  151 
lor  heating  sys.  definitions,  86 
system    for   automatic  control  of 

Webster  system,  147 
Pitot  tubes,  33 
Plans  and  speci.  for  htg.  sys.,  318 

typical  specifications,  319 
Plenum    system,    actual   amount   of 

air  exhausted  in,  188 
air  needed  cu.  ft.  per  hour  in,  172 
air  velocity  , table,  186 
air  velocity  theoretical  in,  184 
air  washing  and  humidifying,  167 
amount  of  steam  condensed,  183 
application  of  to  school  bldgs.,  200 
approximate  rules  for,  178 
approximate  sizes  of  fan  wheels, 

table,  195 

arrangement  of  coils  in  pipe  heat- 
ers, 180 
arrangement  of  sees,  and  stacks  in 

Vento  heaters,  182 
basement  plans  for,  203 
blower  fans,  actual  h.  p.  to  move 

air,  193 

Carpenter's  rules  for,  194 
cast  surface  for,  161 
coil  surface  in,  173 
cross  sectional  area  ducts,  regis- 
ters, etc.,  172 
data,  table,  202 
division  of  coil  surface  in,  162 
double  ducts  in,  166 
dry  steam  needed  in  excess  of  exh. 

from  engine,  183 

efficiency  and  air  temp.,  table,  175 
factors  for  change  of  velocity  and 

volume,  table,  188 
fan  drives  for,  195 
final  air  temperature  in,  179 
floor  plans  for,  203-205 
heating  surface  in  coils  of,  173 
heating  surfaces,  159 
h.  D.  of  engine  for  fan  for,  192 
h.  p.  to  move  air,  table,  186 
'K,'  values  of,  174 
layout,  163,  164 
piping  connections  around  heater 

and  engine,  200 
pressure  and  velocity,  results  of 

tests  of,  189 


single  duct  in,  165 

speed  of  blower  fans,  table,  197 
!     speed  of  fans  for,  196 

temp,  of  air  at  register  in,  171 

temp,  of  air  leaving  coils,  180 

total  B.  t.  u.  transmitted  per  hr., 
table,  176 

use  of  hot  water  in  indirect  coils, 
183 

values  of  'c,'  176 

values  of  'K,'  174 

velocity  of  air  escaping  to  atmos 
phere,  table,  187 

work  done  in  moving  air,  192 
Power  plant  layout,  259 
Pressed  steel  radiators,  103 
Pressure,  absolute,  12 

and  velocity,  results  of  tests,  189 

gage,  12 

in  ounces  per  sq.  in.,  table,  356 

water  in  mains,  231 
Principal  features  of  mechanical  vac- 
uum heating  system,  143 
Properties  of  air,  table,  344 

of  ammonia,  table,  380 

of  carbon  dioxide,  table,  382 

of  steam,  table,  335 

of  sulphur  dioxide,  table,  382 
Psychometric  chart,  345 
Pumps,  boiler  feed,  249 

centrifugal,  247 

circulating,  244 

city  water  supply,  249 

electric,  137 

for  absorption  system,  301 

for  mech.  vac.  steam  heating,  144 

Radiation,  14 

amount   of,   one   sq.    ft.    reheater 
tube  surface  will  supply,  241 

amt.  supplied  by  economizer,  253 

amt.  supplied  by  one  h.  p.,  252 

hot  water,  106 

one  Ib.  exh.  steam  will  supply,  237 

supplied  by  1  h.  p.  exh.  steam,  237 

sur.  to  heat  circulating  water,  254 

surface  to  heat  feed  water,  255 
Radiators,  amt.  of  surface  on,  108 

cast,  103 

classification  of,  104 

columns  of,  104 

direct,  87 

direct-indirect,  87 

height  of,  106 

indirect,  88 

location  and  connection  of,  124 

pipe  coil,  104 

pressed  steel,  103 

sizes,  etc.,  for  ten  room  house, 
table,  127 

sizes,  table  of,  108 

steam,  106 

surface  calculation  for,  114 

sur.  effect  on  trans,  of  heat,  107 

tapping  list,  358 


400 


INDEX 


Recirculating  duct,  72 
Rectifiers,  298 
References, 

district  heating,  270 

electrical  heating,  282 

furnace  heating,  84 

heat  loss,  50 

hot  water  and  steam  heating,  139 

plenum  heating,  206 

vacuum  heating,  152 

ventilation  and  air  supply,  38 

refrigeration,  318 
Refrigeration, 

absorbers,  300 

absorption    and    compression    sys- 
tems compared,  302 

absorption  system,  294 

absorption  system,  elevation  of, 
296 

capacity  of  brine  cooled  system, 
315 

capacities,  table,  385 

circulating  system,  302 

classification  of  systems,  283 

coils,  sq.  ft.  cooling,  311 

cold  air  system,  284 

compression  system,  286 

condenser,  289 

coolers  for  weak  liquor,  301 

costs  of  ice  making,  316 

evaporators,  292 

exchangers,  301 

gallon  degree  calculation,  315 

general  application,  313 

generators,  298 

horse-power  for,  384 

heat  loss,  308 

ice  making  cap.  calculation,  314 

influence  of  dew  point,  305 

methods  of  maintaining  low  temp., 
303 

pipe  line,  306 

pipes,  valves  and  fittings,  294 

pump  for  absorption  system,  301 

rectifiers,  298 

vacuum  system,  284 
Register,  area  of,  56 

dimensions  of,  table,  350 

ducts,  area  of,  172 

sizes,  net  heat,  56 

temperature,  56 
Regulation,  district  heating,  263 

Sylphon  damper,  273 
Room  temperature,  standard,  47 

Salt  brine  solution,  384 
Service  connections,  235 
Sheet  metal  dimensions,  353 
Single  duct,  plenum  system,  165 
Sizes  of  fan  wheels,  approximate, 

table,  195 

Sizes  of  ice  cans,  389 
Smoke  flues,  equalization  of,  350 
Specifications  for  plans,  319 
for  boilers,  371 


Specific  heat,  13 

heats,  etc.,  of  substances,  355 
Speeds  of  blower  fans,  196 
Squares,  cubes,  etc.,  table,  328 
Stacks  and  risers,  74 
Standard  room  temperature,  47 
Steam  and  hot  water  fittings,  110 

available  for  heating  circulating 
water,  237 

boilers,  108 

condensed    per   sq.   ft.   of  heating 

sur.  per  hour,  plenum  sys.,  183 
I     dry,  heeded  in  excess  of  engine  ex- 
haust, 183 

heater,  high  pressure,  244 

heating,  district,  264 

loop,  135 

mains,  diameter  of,  265,  362 

pipe  fittings,  366 

pipe  insulation,  131 

radiators,  106 

traps,  high  pressure,  134 

used  by  engines,  375 
Steam  system,  85 

amt.  condensed  in  plenum  sys.,  183 

classification,  87 

diagrams  for,  91 

parts  of,  85 

second  classification  of,  88 
Street  mains  and  conduits,  layout, 

218 

Suggestions   for  operating  furnaces, 
78 

hot  water  heaters  and  boilers,  137 
Sylphon  damper  regulator,  273 

Table  1  determination  of  COs,  21 
Tables  II,  III  volume  of  air  per  per- 
son, 23,  24 
Table  IV  conductivities  of  materials, 

40 

Table  V  exposure  losses,  44 
,  Table  VI  values  of  t',  48 
!  Table  VII  values  of  to,  49 
!  Table  VIII   heat   given   off   by   per- 
sons, lights,  etc.,  49 
I  Table  IX  application  to  10  room 

res.,  63 

;  Table  X  size  and  sur.  of  rads.,  108 
Table  XI  temp,  of  water  in  mains, 

120 

Table  XII  summary,  h.  w.  htg.,  127 
'  Table  XIII  vel.  in  plenum  sys.,  172 
Tables  XIV-XVII  efficiencies  of  coils, 

175,  177 
Tables  XVIII-XIX  temp,   of  air   on 

leaving  coils,  179,  180 
Tables  XX-XXII  air  pressure  and 

velocity,  186,  188 
i  Table  XXIII  sizes  of  fans,  195 
!  Table  XXIV  speeds  of  fans,  197 
Table  XXV  data  for  plenum  sys.,  202 
Table  XXVI  heat  loss  from  pipes,  217 
Table  XXVII  pressure  of  water  in 
mains,  234 


INDEX 


401 


Table  XXVIII  cal.  of  conduit  mains, 

269 
Table  XXIX  transmission  through 

insulation,  309 

Table    1  squares,  cubes,  etc.,  328 
Table    2  trigonometric  functions,  334 
Table    3  equivalents  of  units,  334 
Table    4  properties  of  steam,  335 
Table    5  Naperian  logarithms,  338 
Table    6  water  conversion  factors, 

338 

Table    7  vol.  and  wt.  of  dry  air,  339 
Table    8  weight  of  pure  water,  340 
Table    9  boiling  points  of  water,  342 
Table  10  wt.  of  water  and  air,  342 
Table  11  relative  humidities,  343 
Table  12  properties  of  air,  344 
Table  13  dew  points  of  air,  345 
Table  14  fuel  value  of  Am.  coals,  348 
Table  15  capacities  of  chimneys,  349 
Table  16  equalization  of  smoke 

flues,  350 

Table  17  dimensions  of  registers,  350 
Tables  18,  20  cap.  of  fur.,  351,  352 
Table  19  cap.  of  pipes  and  reg.,  351 
Table  21  area  of  vertical  flues,  352 
Table  22  sheet  metal  dimensions,  353 
Table  23  weight  of  G.  I.  pipe,  354 
Table  24  sp.  ht.,  etc.,  of  substances, 

355 

Tables  25,  26  water  pressures,  356 
Table  27  wrought   iron  pipes,  357 
Table  28  expansion  of  pipes,  358 
Table  29  tapping  list  of  rad.,  358 
Table  30  pipe  equalization,  359 
Table  31  cap.  of  hot  water  risers,  360 
Table  32  cap.  of  steam  pipes,  360 
Table  33  cap.  of  hot  water  pipes,  361 
Table  34  cap.  of  hot  water  mains,  361 
Tables  35,  36  sizes  of  steam  mains,  362 
Table  37  friction  in  pipes,  364 
Table  38  grav.  and  vac.  returns,  365 
Table  39  expansion  tanks,  365 
Table  40  sizes  of  flanged  fittings,  366 
Table  41  dimensions  of  pipe  fittings, 

Table  42  friction  in  air  pipes,  367 
Table  43  temp,  for  testing  plants, 

370 

Table  44  spec,  for  boilers.  371 
Table  45  heat  trans,  through  pipe 

covering,  372 

Table  46  factors  of  evaporation,  373 
Table  47  heat  in  feed  water,  373 
Table  48  sizes  of  Vento  heaters,  374 
Table  49  steam  used  by  engines,  375 
lables  50,  51,  52  speeds,  cap.,  h.  p. 

of  various  fans,  376-378 
Table  53  freezing  mixtures,  380 
Table  54  properties  of  ammonia,  380 
Table  55  sol.  of  ammonia  in  water, 

381 
Table  56  strength  of   ammonia 

liquor,  381 


Table  57  properties  of  sulphur  diox- 
ide, 382 

Table  58  properties   of  carbon  diox- 
ide, 382 

Table  59  boiling  points  of  liquids,  383 
Table  60  calcium  brine  solution,  383 
Table  61  salt  brine  solution,  384 
Table  62  horse-power  for  refrig.,  384 
Table  63  ammonia  for  one-ton  re- 
frig.,  385 

Table  64  refrigeration  caps.,  385 
Table  65  cost  of  ice  making,  386 
Table  66  temperature  of  ammonia, 

387 

Table  67  hydrometer  scales,  388 
Table  68  time  to  freeze  ice,  389 
Table  69  sizes  of  ice  cans,  389 
Table  70  temp,  for  cold  storage,  389 
Tanks,  expansion,  113,  365 
Temperature  absolute,  12 

best  for  design,  79 

chart,  81 
Temp,  control  in  heating  sys.,  271 

Andrews  system,  272 

important  points  in,  275 

in  large  plants,  274 

Johnson  system,  276 

National  system,  278 

Powers  system,  277 

principle  of  system,  271 

special  designs  of,  275 

Sylphon  damper  control,  273 

thermostat,  272 

of  air  entering  plenum  system,  171 

of  air  in  greenhouses,  table,  120 

of  air  leaving  coils  in  plenum  sys- 
tem, 179 

of  ammonia,  387 

for  cold  storage,  389 

for  testing  plants,  370 

measurement  of  high,  11 

methods  of  obtaining  low,  303 

room  standard,  47 
Thermofiers,  Belvac,  148 
Thermostat,  272 

thermostatic  valve,  146 
Time  to  freeze  ice,  389 
Traps,  high  pressure  steam,  134 

low  pressure  steam,  133 
Trigonometric  functions,  334 

Under-feed  furnaces,  69 

Use  of  hot  water  in  indirect  coils,  183 

Vacuum  systems,  99 

and  gravity  returns,  365 

of  refrigeration,  284 
Values  of  'c,'  176 

of  'k,'  177 

of  'n,'  47 

of  %'  48,  49 
Valves,  air,  112 

automatic  vacuum,  149 

modulation  valve,  147 


402 


INDEX 


thermostatic,  146 

types  of,  111 

Velocity  of  air  by  application  heat, 
31 

of  air  escaping  to  atmosphere,  187 
Vent  registers  (net),  57 

stacks,  58 
Ventilation  heat  loss,  44 

air  required  per  person,  21 
Vento  coils,  values  of  'k'  for,  177 
Vento  heater  sizes,  374 
Vertical  hot  air  flues,  table,  352 
Volume  and  wt.  of  dry  air,  table,  339 

Warm  air  fur.,  cap.  of,  table,  351 

air  heating  cap.,  352 
Washing  and  humidifying  of  air,  167 


Water,  conversion  factors,  table,  338 

hammer,  133 

needed  per  hour  in  dist.  htg.,  230 

pressure  in  mains,  231 

pressure,  table  of,  234 

seal  motor,  Webster,  145 

weight  of  column  corresponding  to 
air  pressure  in  ozs.,  356 

weight  of  pure,  table,  340 

weight  of  water  and  air,  table,  342 
Webster  system  of  vac.  heating,  145 
Weight  of  pure  water,  340 
Weight  of  G.  I.  pipe,  354 

of  water  and  air,  table,  342 
Work  done  in  moving  air,  192 
Wrought  iron  and  steel  pipes,  table, 
357 

expansion  of,  table,  358 


OUTLINE 


A  COURSE  OF  INSTRUCTION 
FOR  TECHNICAL  SCHOOLS 


WITH 


QUESTIONS  AND  PROBLEMS 


TO  BE  USED  IN  CONNECTION 
WITH  THE 


HANDBOOK 


HEATING  AND  VENTILATING 
ENGINEERS 

HOFFMAN 


SUGGESTIONS  FOR  A  COURSE  OF  INSTRUCTION. 

Preparation  for  the  Course: — In  adapting  this  sub- 
ject to  a  college  course,  it  should,  if  possible,  be  taken  up 
during  the  last  year  of  college  work,  when  the  istudent  can 
have  the  benefit  of  a  large  part  of  the  training  in  Heat, 
Thermodynamics,  Engineering  Design  and  Steam  Engines 
and  Boilers,  all  of  which  subjects  are  of  great  value  in 
heating  and  ventilating  work.  The  ^subjects  of  Heat  and 
Thermodynamics  prepare  for  analytical  and  experimental 
investigation  in  heat  transference,  while  a  knowledge  of 
engines,  boilers  and  general  machinery  gives  information 
of  a  more  practical  turn,  the  application  of  which  is  neces- 
sary in  heating  design.  A  course  of  'Study,  as  Outlined  here, 
is  primarily  theoretical  but  it  should  not  stop  there.  To 
be  of  service  in  fitting  a  man  for  active  participation  in  the 
work  after  leaving  school,  it  must  emphasize  such  points 
as  relate  to  the  layout  of  the  drawings  and  to  the  mate- 
rials used  in  the  'Construction  as  well.  A  course  fitted  to 
practical  needs  should  not  only  require  a  full  set  of  cal- 
culations for  each  design,  but  it  should  require  a  complete 
layout  of  each  system. 

Administration  of  the  Work: — The  course  should  be 
administered,  part  in  the  class  room,  as  lectures  and  reci- 
tations, and  part  (a  set  of  designs)  should  be  left  to  the 
student  to  work  up  largely  upon  his  own  responsibility  and 
submit  the  same  for  approval. 

The  work  in  the  class  room  should  be  at  .least  two 
hours  per  week,  and  may  be  divided  between  lectures  and 
recitations  in  whatever  manner  is  thought  best.  In  the  lec- 
tures, references  should  be  made  to  the  various  authorities 
on  iheating  and  ventilating  with  suggestions  that  these 
authorities  be  looked  up.  The  lectures  should  also  include 
very  full  'details,  concerning  the  laying  out  of  such  work, 
with  suggestions  concerning  'the  proper  .selection  of  ma- 
terials. The  recitations  should  be  made  as  practical  as 
possible  to  serve  in  bringing  out  the  points  that  would 
probably  be  confusing  in  developing  the  designs.  All  class 
room  work  should  be  timed  to  suit  the  design  under  con- 
sideratio,n,  otherwise  the  design  work  and  the  class  room 
work  will  be  independent  rather  than  mutually  helpful. 


4.  HEATING  AND  VENTILATION 

Outline  of  the  Work  of  Design: — After  two  or  three 
weeks  devoted  to  the  subjects  of  ventilation,  radiating  sur- 
faces, etc.,  the  work  of  design  should  be  taken  up  and  might 
very  properly  cover  the  following  systems  of  heating: 

1.  Furnace  heating,  as  applied  to  residences.     Time  al- 
lowed, three  weeks. 

2.  Hot   water   heating,   as   applied   to   residences.      Time 
allowed,  three  weeks. 

3.  Steam   heating,    as  applied   to    residences.      Time    al- 
lowed, two  weeks. 

4.  Plenum   system   of   warm   air   heating,    as   applied   to 
schools    and     low     office     buildings.       Time    allowed, 
four  weeks. 

5.  District    heating    from   a    central    station.      Time    al- 
lowed, four  weeks. 

The  above  will  be  found'  to  cover  the  heating  and 
ventilating  work  very  thoroughly.  If  the  subject  of  refrig- 
eration be  taken  up  as  a  part  of  the  'half  year's  work,  the 
instructor  must  sacrifice  that  part  of  the  above  which  he 
deems  of  least  importance.  The  work  sihould  be  admin- 
istered in  such  a  way  as  to  remove  as  much  of  the  purely 
routine  work  as  possible,  otherwise  the  course  which 
is  planned  for  one-half  year's  work  would  be  too  long 
for  the  time  allowed  to  the  average  student  by  the 
school  curriculum.  As  an  illustration,  the  student  pre- 
pared for  this  work  is  fairly  well  qualified  to  make 
mechanical  drawings,  and  any  relief  which  can  be 
given  from  drawing  work  will  permit  the  equivalent  time 
being  put  upon  other  and  more  important  parts  of  the  de- 
sign. This  relief  can  take  the  form  of  prepared  building 
plans  stamped  off  on  standard  siz-ed  paper,  thus  permitting 
the  insertion  of  heating  drawings  on  the  same  pages  without 
the  routine  labor  of  reproducing  an  entirely  new  set  of 
drawings.  These  plans  may  be  made  the  same  size  as  the 
blanks  upon  which  the  calculations  are  submitted,  say  8% 
x  11  inches  and  should  always  be  different  from  any  pre- 
viously given.  The  final  report  will  then  include  every 
thing  under  one  cover  and  can  be  filed  away  without  dif- 
ficulty. For  sample  set  of  building  plans,  see  Figs.  14,  15 
and  16,  with  the  furnace,  pipes  and  registers  removed. 

Speeifications: — It  is  desirable  that  each  man  have 
experience  in  writing  specifications  for  his  own  plans.  This 
is  difficult  for  a  beginner  and  requires  considerable  time  to 
do  properly.  It  is  thought  best,  therefore,  to  present  a  brief 


QUESTIONS    AND    PROBLEMS  5 

set  of  specifications  (see  Chaper  XVIII)  to  show  how  such 
work  is  done  and  let  this  set  be  used  to  give  suggestions 
for  the  more  complete  set.  Originality  in  form  and  sim- 
plicity and  accuracy  of  statement  are  the  principal  points 
to  be  observed.  The  instructor  will  use  his  own  discretion 
in  deciding  how  comprehensive  these  specifications  shall  be. 

INSTRUCTIONS  FOR  DESIGN   REPORTS. 

Nos.   1,   2  and  3. 
Furnace,  Hot  Water  and  Steam  Systems. 

The  first  three  design  reports  in  heating  and  ventila- 
tion cover  three  lines  of  residence  heating,  i.  e.,  furnace, 
hot  water  and  steam.  Three  complete  sets  of  plans  of  the 
same  house  are  supplied  to  each  member  of  the  class,  upon 
which  the  heating  designs  may  be  made.  With  these  dupli- 
cate plans,  the  heat  loss  need  be  calculated  once  only  for  the 
three  designs.  Upon  submitting  report  No.  1,  a  copy  of  the 
heat  loss  should  be  made  to  use  on  Nos.  2  and  3. 

Each  man  shall  submit  designs  which  he  has  himself 
worked  up.  No  objection  will  be  raised  to  two  or  more 
students  working  simultaneously,  checking  each  other's 
figures  and  in  a  general  way  profiting  by  good  suggestions. 
It  is  objectionable,  however,  to  divide  the  work  so  that  each 
man  does  only  a  part.  Designs  that,  in  the  opinion  of  the 
instructor,  have  been  copied,  will  .be  rejected  and  marked 
zero. 

Each  design  will  be  submitted  in  a  manilla  cover 'prop- 
erly filled  out  with  the  name  of  the  designer,  the  name  of 
the  design  and  the  date.  If  the  design  was  worked  up  in 
conjunction  with  any  other  person  or  persons,  these  names 
should  be  given. 

For  the  convenience  of  the  instructor,  each  report  will 
be  arranged  as  follows: 

1.  Blank  sheet  for  instructor's   corrections. 

2.  Title  page  with  statement  of  the  design. 

3.  Specification  sheets. 

4.  Plans;   basement,    first  floor  and  second  floor. 

5.  iSummary  table,  after  the  pattern  of  Table  IX. 

6.  Calculations  and   notes. 

The  reports  are  returned  after  correction. 

The  calculations  in  the  furnace  design  will  include,  for 
each  room,  the  heat  loss,  the  cubic  feet  of  air  needed  for  each 
room  as  a  heat  carrier  (this  should  be  checked  for  ventila- 


6  HEATING   AND    VENTILATION 

tion),  the  heat  loss  (by  formula),  the  cubic  feet  of  air  needed 
per  hour  and  the  areas  of  the  net  registers,  gross  registers, 
stacks  and  leaders;  also,  for  the  entire  plant,  the  air  supply 
ducts  and  the  grate.  Specify  the  type  and  size  of  the  fur- 
nace installed. 

The  calculations  in  the  hot  water  design  will  include  the 
heat  loss,  the  radiation  in  square  feet  per  room,  the  radiator 
pipe  sizes,  the  riser  pipe  sizes,  the  sizes  of  the  general  mains 
(show  on*  plans),  the  'gallons  of  water  heated  per  hour,  the 
size  of  the  expansion  tank  (locate  on  plans)  and  the  type  and 
size  of  the  heater  installed. 

The  calculations  in  the  steam  design  will  include  the  heat 
loss,  the  radiation  in  square  feet  per  room,  the  radiator  pipe 
sizes,  the  riser  pipe  sizes,  the  sizes  of  the  general  mains 
(show  on  plans),  the  total  pounds  of  steam  condensed  per 
hour  and  the  type  and  size  of  the  boiler  installed. 

In  drawing  the  mains  on  the  plans  and  in  making  the 
riser  layout,  use  the  notations  as  given  in  this  pamphlet. 
Use  arrows  to  denote  the  direction  of  flow  within  the  pipes. 

The  reports  will  be  submitted  as  follows: 

No.  1 19 

No.  2 19 

No.  3 19 

INSTRUCTIONS  FOR  DESIGN  REPORT. 

No.  4. 
Plenum  Warm  Air  System. 

These  instructions,  together  with  the  three  building 
plans  (not  shown  here  but  same  as  Figs.  104,  105  and  106 
with  the  heating  plans  removed),  will  form  the  basis  upon 
which  to  design  a  plenum  system  of  warm  ai.r  heating  for 
the  /building  shown.  Each  room  is  numbered  and  should 
be  referred  to  in  the  report  by  that  number.  The  heat  loss 
for  each  floor  will  be  estimated  from  some  acceptable 
formula.  If  Carpenter's  formula  is  used,  take 

Basement,     (walls    only    two-thirds    exposed),     n  =  1. 

First  floor,   (walls  fully  exposed),  n  =  l1/^. 

Second  floor,   (same  as  first  floor). 

Corridors,  n  =  2. 

In  the  calculations  the  following  points  should  be 
worked  up  for  each  room:  the  heat  loss,  the  cubic  feet  of 
air  per  hour  as  a  heat  carrier  (this  should  then  be  checked 


QUESTIONS    AND   PROBLEMS  7 

for  ventilation  and  the  maximum  requirement  taken),  the 
net  area  of  the  register  in  square  inches,  the  catalog  size 
of  the  register  (as  12x14  inches)  and  the  size  of  the  wall 
duct  (as  8x10  inches).  Find  also  the  following:  the  size  of 
the  fresh  air  entrance;  the  siize  of  the  main  leader  at  the 
plenum  •chamber  and  the  sizes  of  the  principal  branches;  the 
square  feet  of  heating  surface;  the  lineal  feet  of  coils;  the 
net  wind  area  at  the  coils;  the  gross  area  at  the  coils  and 
the  arrangement  of  the  coils  in  sections;  the  horse-power 
and  the  revolutions  per  minute  of  the  fan,  including  the 
sizes  of  the  inlet  and  the  outlet  of  the  fan;  and  the  horse- 
power of  the  engine  installed,  including  the  diameter  and 
the  length  of  the  stroke.  In  addition  to  the  above,  select  one 
of  the  most  important  rooms  and  find  the  temperature  of  the 
air  at  the  registers  when  excess  air  is  required  for  ventjla- 
tion. 

The  principal  work  on  the  plans  will  be  to  lay  out  the 
basement  equipment.  The  engine  and  fan  will  be  placed  in 
room  ....  and  should  contain  all  the  necessary  pieces  of 
apparatus  which  go  to  make  up  the  complete  blower  sys- 
tem. iShow  on  the  plans  the  location  of  the  tempering  and 
heating  coils,  how  the  air  is  taken  from  the  outside  of  the 
building,  is  passed  through  the  blower  into  the  plenum 
chamber  and  thence  through  a  system  of  ducts  to  the  vari- 
ous parts  of  the  'building. 

It  is  understood  that  the  steam  is  to  be  received  at  the 
building  under  a  maximum  gage  pressure  of  30  pounds 
per  square  inch,  and  is  to  be  used  in  the  coils  under  a  pres- 
sure of  not  over  5  pounds  gage.  This  reduction  will  be  ac- 
complished by  the  use  of  a  pressure  reducing  valve.  Arrange 
the  coils  and  piping  so  either  exhaust  steam  or  live  steam 
may  be  used  in  all  the  coils.  Generally  the  exhaust  steam 
from  the  fan  engine  is  used  in  the  tempering  coils  and  live 
steam  in  the  main  heating  coils.  After  estimating  the  total 
amount  of  heating  surface,  divide  this  into  tempering  and 
heating  coils. 

A  back  pressure  valve  should  be  placed  on  the  exhaust 
line  opening  to  the  air  at  the  roof  to  relieve  excessive  back 
pressure  on  the  engine.  Oil  and  steam  separators  should 
also  be  installed. 

It  is  suggested  that  a  separate  plate  be  made  of  the 
heater  room  to  avoid  complications  in  drawing.  This  plate 


S  HEATING  AND   VENTILATION 

should  contain  a  plan  and  elevation  with  all  piping  connec- 
tions and  necessary  valves  clearly  shown. 

Design  No.  4  will  be  submitted 19 

INSTRUCTIONS  FOR  DESIGN  REPORT. 

No.   5. 
Centralized  Hot  Water  or  Steam  System. 

These  instructions  together  with  the  plan  of  the  city, 
Fig.  Ill,  showing  the  portion  of  the  city  to  be  heated,  will 

form  the  basis  upon  which  to  design  a  centralized  

heating  system  for  the  said  locality.  The  plant  will  be  in- 
stalled in  connection  with  the  municipal  lighting  and  pump- 
ing stations  located  at and 

streets.  In  reconstructing  the  present  plant  the  building 
will  not  be  used.  The  equipment,  which  may  be  considered 
as  new,  is  as  follows.  (Italics  indicate  variable  terms). 

1,  250  K.  W.  direct  current  generator,  direct  driven  from  a 
cross  compound,  non-condensing,  slow  speed,  Corliss  engine. 

1,  150  K.  W.  direct  current  generator,  direct  driven  from  a 
simple  non-condensing  high  speed  engine. 

1,  75  K.  W:.  alternating  current  generator,  direct  driven 
from  a  simple,  non-condensing,  high  speed  engine. 

12,  1%  million  gallon,  horizontal  reciprocating  duplex,  city 
water  supply  pumps,  size  14  and  20  x  12  x  10  inch.  When  the 
pump  is  in  action,  the  pressure  head  against  the  pump  is  55' 
pounds  and  the  suction  head  is  10  pounds  per  square  inch. 

The  small  apparatus  in  the  plant  requiring  steam  (boil- 
er feed  pumps,  etc.)  may  be  assumed  at  15  per  cent,  of  the 
total  steam  consumption  of  the  large  units. 

3,  250  H.  P.  water  tube  boilers  -are  at  present  supplying 
the  plant  with  steam. 

If  a  hot  water  system  is  used,  pumps  will  be  installed 
to  circulate  the  .hot  water  in  the  heating  system.  This  will 
necessitate  an  enlargement  of  the  present  steam  boiler 
plant.  In  addition  to  this,  extra  .boiler  service  may  be 
necessary  to  be  used  as  heaters  or  steamers  for  the  heating 
system  to  make  up  for  the  deficiency  of  exhaust  steam.  The 
heating  capacity  of  the  system  should  be  limited  to,  say  125000 
square  feet  of  steam  radiation,  or  187500  square  feet  of  hot 
water  radiation. 


QUESTIONS    AND    PROBLEMS  9 

Only  that  Rart  of  the  city  shown  between  the  dotted 
lines  will  be  considered  desirable  heating1  territory.  Allow, 
say  9000  square  feet  of  hot  water  radiation  or  6000  square 
feet  of  steam  radiation  to  the  four  sides  of  a  business  blo<ck 
and  about  half  of  this  to  the  four  sides  of  a,  residence 
block. 

In  working  up  this  design,  investigate  and  plan  for  the 
following-  points:  the  probable  number  of  square  feet  of 
heating  surface  in  the  district;  the  layout  of  the  street 
mains  With  a  section  of  the  conduit;  the  sizes  of  the  mains 
at  the  plant  and  at  several  distant  points  in  the  system, 
the  number  and  sizes  of  the  circulating-  pumps;  the  load 
curve  of  the  plant  and  the  amount  of  exhaust  steam  per 
hour  available;  the  size  of  and  the  square  feet  of  heating 
surface  in  the  exhaust  steam  heaters  for  the  circulating 
system,  if  used;  the  total  boiler  horse-power  and  'how  it  is 
divided  into  units;  the  total  economizer  surface  and  how  it 
is  divided  into  units;  the  chimney  diameter  and  height,  and 
the  complete  layout  of  the  plant  including  the  arrangement 
of  the  engines,  boilers,  pumps,  heaters,  pipes,  etc. 

Design  No.   5  will  be  submitted..  ..19.. 


10 


HEATING   AND    VENTILATION 


NOTATIONS   TO   BE  USED   IN   DRAWING'S. 
Wihen  making  drawings  it  is  recommended  that  the  fol- 
lowing symbols  be  used. 

— — — — — - — — — — — — —      Steam  line. 

—  —  —  ———  —  ——  — —  —     Return  line. 

Exhaust  steam  line. 

Water  line. 

Air  line. 

Globe,  gate  and  check 

valves. 

Pressure  reducing,   back 
'  pres.   and  angle  valves. 
Trap,    steam   separator  and 

union.  (size 

Reducing    fitting,    flow    and 
Expansion  joint  and  anchor. 

Tee  and  ell. 

Long  radius  fittings. 


Expansion  tank  and  drop. 
Radiator    and    thermo,static 
regulator. 

Damper  regulator. 


Fresh  and  foul  air. 
Vent  and  heat  stacks. 

Vent  and  heat  registers. 
Deflecting  damper. 

Volume  and  mixing 


u 

h. 

i+ 

A 

3 

\     \ 

o 

r    A 

l^. 

H 

HVv^ 

£3- 


\     / 


M 

pn    F 

IJJ 

Motor  and  fan. 

PR 

Belt  drive. 

i  i.. 

lj\  }           • 

T                                                    .                . 

B 

Boiler  and  eng 

$  0 


Square  feet  and  square 
inches. 


QUESTIONS    AND    PROBLEMS.  11 

QUESTIONS   AND  PROBLEMS 

CHAPTER    I. 

t 

1.  (a)    Name    two    units    used    in   measuring    degree    of 
heat  and   state   how   each  was   originally   devised. 

(b)    Name    two    units    used    in    measuring    quantity 
of   heat   and   define   each. 

2.  (a)    Change    the   following   Fahrenheit   temperatures 
to  Centigrade  temperatures.     0  deg.,  32  deg.,  60  deg. 

(b)    Change    the    following   Centigrade    temperatures 
to  Fahrenheit  temperatures.     100  deg.,  — 40  deg.,  — 273  deg. 

3.  'Required  to  determine  the  temperature  of  a  furnace 
above  600  degrees  F.    Name  four  types  of  pyrometers  which 
may  be  used. 

4.  What    is    the    temperature    of   absolute    zero    on    the 
Fahrenheit  scale?     Show  how  it  was  determined. 

5.  Into  a  duct  of  uniform  cross  section  air  is  entering 
at  the   rate   of   15   feet  per   second.     In   its  passage   through 
the    duct   its   temperature    is    raised   from   0    deg.    to    92    deg. 
What  would  be  the  increased  velocity  beyond  the   point   of 
heating? 

6.  Define  gage  pressure,  absolute  pressure  and  specific 
pressure. 

7.  Two   tons   of   water   were   raised   from   60   deg.   F.    to 
212  deg.  F.  in  one  hour.     What  was  the  equivalent  mechani- 
cal horse-power? 

8.  Name  three  ways  in  which  heat  may  be  transmitted, 
,     and   show   the    distinguishing   features    of   each   method. 

»  - 

CHAPTER   II. 

9.  Show  W'hat  effect  respiration  has  upon  pure  country 
air,  by  stating  percentages  of  the  constituents  of  air  before 
and   after    breathing. 

10.  How  many  parts  >of  CO2   in  10000  parts   of  air  is   it 
safe   to  allow  in  the  air  of  a  room? 

11.  (a)    Explain  a   method   by   which   the   percentage   of 
CO2  in  air  may  be  determined  approximately. 

(b)  If  exact  percentage  of  O,  CO,  CO2  and  N  are  re- 
quired, what  method  would  be  used? 

12.  Assuming    the    average    respiration    to    be    20    cubic 
Inches  of  air  and  that  there  are  20  respirations  per  minute, 
show  the  number  of  cubic  feet  of  CO2  each  person  exhales 
into   a   room   per   hour. 


12  HEATING    AND    VENTILATION 

13.  If  the  cubic  feet  of  CO2  per  person  per  hour  is  .6 
and  the  allowable  CO2  in  the  room  is  to  be  not  more  than 
8  parts  in  10000  ,parts  of  air,  with  pure  air  containing  4 
parts  'Of  CO2  in  10000  parts  of  air,  find  the  number  of  cubic 
feet  of  fresh  air  which  should  be  allowed  per  person  per 
hour. 

',•  14.  Explain  what  is  meant  by  humidity  and  show  how 
it  affects  the  comfort  of  persons. 

*•  15.  Define  and  distinguish  between  actual  humidity  and 
relative  humidity. 

16.  Describe  a  wet  and   dry  bulb   hygrometer  and   show 
how  it  is  used  to  find  relative  humidity. 

17.  What  precautions   should  be   observed   in   the   use   of 
any  wet  and  dry  bulb  hygrometer? 

18.  Using  the  hygrometric  chart,  having  given. dry  bulb 
100  deg.  and  wet  bulb  80  deg.,  find  relative  humidity,  abso- 
lute  humidity   and   dew  point   for   the   room   air.      Check   by 
tables   and    calculations. 

19.  With    an    absolute   humidity    of   4    grains   and   a    dry 
bulb  temperature  of  60  degrees,  what  should  be  the  reading 
of  the  wet  bulb  thermometer?     Check. 

20.  Wiith  an  absolute  humidity  of  4  grains  and  a  relative 
humidity  of  50  per  cent.,  what  are  the  temperatures   of  the 
wet  and  dry  bulb  thermometers?     Check. 

21.  If  a  ventilating  system  takes   in  10000  cubic  feet  of 
air  per  hour  at  an  average   temperature   of   52   deg.   and  an 
average    humidity    of    60    per   cent.,    and    before    delivery    to 
rooms   it   is   to   be   heated   to   an   average   temperature   of   72 
deg.,  how  much  moisture  must  be  supplied  per  hour  to  the 
air  if  ithe  humidity  is  to  be  kept  constant  at  60  per  cent? 

22.  If  an   enclosed  body  of  air  be  heated  from  0  deg.   to 
70    deg.,    without    change    of    volume,    would    its    actual    hu- 
midity and   its  relative  humddity  be  increased   or  decreased 
and  why? 

23.  Explain   two   methods   for   obtaining   the   velocity    of 
an   air   current. 

24.  A  furnace  chimney  is  18  in.  X  18  in.  X  35  ft.     If  the 
average  temperature  of  the  gases  is  200  deg.  and  the  outside 
temperature   is   40   deg.,   find   the  theoretical   velocity   of  the 
gases  up  the  chimney. 

25.  How   much    coal    per   hour   would    be    burned    on    the 
grate  connected  to  the  above  chimney  if  the  actual  veloqity 
up  the  chimney  were  one-half  the  theoretical? 


QUESTIONS  AND  PROBLEMS  13 

CHAPTER  III. 

" 

26.  How  many  cubic  feet  of  air  may  be  heated  through 
one  degree  F.,  by  one  B.  t.  u.  ? 

27.  A  first  floor  living  room  15  ft.  X  20  ft.,  ceiling  10  ft. 
has   four   exposed  windows   each   24   sq.    ft.      It   has   two  ad- 
jacent  walls    exposed,   a   15    ft.    side   to   the   north  and   a   20 
ft.    side    to    the    west.      Calculate    the    heat   loss    by    Carpen- 
er's    formula    with    a   room    temperature    of    70    deg.    and   an 
outside   temperature   of  —  20   deg.     Walls   are   those   of  the 
average  wooden  dwelling.     Make  no  allowance  for  exposure. 

28.  (Calculate  problem  27  by  formula   (11)   and  compare. 
Take  a  =  0  and  n  =  2;  also  single  windows  and  no  unheated 
space    adjacent. 

29.  A  second  floor  lecture  room  in  a  university  building 
is   72   ft.   X   52  ft.,  ceiling  15   ft.     There  are   twelve  windows 
each  30  sq.  ft.,  also  one  side  72  ft.  long  and  two  sides  each 
52   ft.  long  exposed,   the  longer  side  to  the  west.     Calculate 
the  heat  loss  by  Carpenter's  formula.     Maximum  inside  tem- 
perature is   65   deg.  and  minimum  outside  temperature  is  — 
15  deg.   (n  —  1  ) 

30.  The   auditorium   of   an    opera   house   measures    80    ft. 
X   90  ft.   with  55   ft.   ceiling.     One   80  ft.   side  .and  two  90  ft. 
sides  are  exposed,  the  shorter  side  .to  the  .south.     Total   ex- 
posed  glass   surface    is    430    sq.    ft.     Calculate    the   heat   loss 
by   Carpenter's   formula,    if   maximum   inside   temperature   is 
65    deg.,    and    minimum    outside    temperature    is    --    20    deg. 
(n  =    .5) 

31.  In  problem  30  the  .auditorium  with  its  balconies  and 
galleries     will     accommodate    a    maximum    of    3000    adults. 

.  What  per  cent,  of  the  radiated  heat  loss  of  the  building 
will  the  bodies  of  the  audience  supply  if  the  rate  is  400 
B.  t.  u.  per  hour  per  person? 

32.  In  problem  29  the  maximum  capacity  of  the  lebture 
room    is    400    persons.      The    room    is    ventilated    with    fresh 
outside  air  at  the   rate   of  1500   cu.   ft.  per  person  per  hour. 
Find  the  total  heat  loss,  H  +  Hv. 

33.  In  problems   30  and   31   the  auditorium   is   ventilated 
at   the   rate   of   1500   cu.   ft.    of  air  per  person   per   hour,   all 
air    being    taken    from    outside    before    being    heated.      Find 
the  total   heat  loss  H  +  Hv. 

CHAPTER  IV. 

i34.     Name   three  advantages   and   three   disadvantages   of 
the  furnace  system  of  heating. 

35.     State  the  essentials  of  a  furnace  system. 


14  HEATING    AND    VENTILATION 

36.  As  regards  air  circulation,  in  what  two  ways  may  a 
furnace  system  be  installed  and  what  are  the  advantages 
of  each? 

•37.  At  what  temperature  is  the  incoming  room  air  tak- 
en in  calculating  a  furnace  system? 

38.  The  heating  system  in  problem  27  is  a  furnace  with 
cold    air    ducts    so    arranged   as    to    recirculate    all    the    air, 
part  of  the  air  or  none  of  the  air,  according  to  damper  po- 
sition.     Compare    the    cost    of    heating    the    room    under    the 
three  conditions,   if,  in  the  second  case,  enough  fresh  air  is 
used  to  provide  for  five  persons  at  the  rate   of  1800  cu.   ft. 
per  hour  per  person. 

39.  When    running  as   under   the   third   case   in   problem 
38,  show  maximum  number  of  people  provided  with  ventila- 
tion at  the  rate  of  1800  cu.  ft.  per  person  per  hour. 

40.  There  is  provided  for  the  room  in  problem  29,  ventil- 
ation for  400  persons  at  the  rate  of  1500  cu.   ft.  per  person 
per  hour.     The  entire  radiated  heat  loss  is  provided  for  by 
the   dropping   of  the   temperature   of  the  (incoming  ventilat- 
ing air  from  some  temperature   down   to   the   ro.om  temper- 
aure.     At  what  temperature  should  it  enter  the  room? 

41.  For  what  velocities  of  air  would  you  design  the  size 
of  registers?  of  heat  stacks? 

42.  The  total  heat  loss  of  a  residence  is  190000  B.   t.   u. 
inclusive   of  ventilation.     It   is  heated  by  a.  furnace   system 
with  average   grade   of  coal   of  about   13000   B.   t.   u.   per  Ib. 
System    provided    with    chimney    such    that    five    pounds    of 
coal  per  hour  per  sq.  ft.  of  grate  is  a  maximum.     Calculate 
the   minimum   size    of   the   grate,    if   furnace    is    60    per   cent, 
efficient. 

43.  Select  a  furnace  for  a  residence  having  a  total  heat 
loss  of  200000  B.  t.  u.  per  hour,   if  Big  Muddy,  Illinois,  coal 
(Table  14)   is  to  be  burned.     Assume  efficiency  of  furnace  at 
60  per  cent,  and  that  seven  pounds   of  coal   are  burned  per 
sq.  ft.  of  grate  per  hour  .  Also  find,   (Table  18)  what  volume 
such  furnace  is  capable  of  heating  in  zero  weather. 

44.  (a)  A  furnace  heated  residence  maintained  at  70  deg. 
Inside,  has  a  total  heat  loss   of  138000  B.   t.   u.   per  hour  on 
a  zero  day.     The  furnace  has  a  24  inch  grate,  and  burns  five 
pounds   of  Indiana  Block  coal  per  sq.   ft.  grate  per  hour  in 
zero  weather.     What  is  the  efficiency  of  the  plant? 

(b)  What  should  be  the  winter's  expense  for  fur- 
nace coal  if  it  costs  $3.50  a  ton,  the  average  outside  tem- 
perature for  the  seven  heating  months  is  32  deg.,  and  the 
above  efficiency  is  constant? 


QUESTIONS  AND  -PROBLEMS  15 

- 

CHAPTER  V. 

45.  Explain  how  the  difficulty  of  heating  the  windward 
room  with  a  furnace   system  may   be   overcome   by   the   use 
of  a   combination   heater. 

46.  Sketch  a  section  through  a  hot  air  furnace  and  show 
path  of  combustion  gases  and  of  the  air  being  heated. 

47.  Distinguish  between  overfeed  and  underfeed  furnaces 
and   give  advantages   and   disadvantages. 

48.  Discuss   thoroughly    the    various    factors    governing 
the  location   of  a  furnace   for   residence   heating. 

49.  Show    the   effects    of   various    locations    of   heat   and 
vent    registers    upon    the    air    movement    of    the    room    and 
show  which  positions  are  considered  best  and  why. 

50.  Explain   the  arrangement    of  apparatus   in   fan-fur- 
nace   heating. 

CHAPTER    VI. 

51.  Compare  steam  and  hot  water  systems  with  furnace 
systems    as    regards    simplicity,    flexibility,    reliability    and 
independence   of  wind  pressures. 

52.  Name  the  principal  parts  composing  a  steam  or  hot 
water  system  of  heating. 

53.  Explain    or    define    the    following1:    headers,    mains, 
branches,     risers,    dry    return,    wet    return,    sealed    return, 
trapped  return. 

54.  Classify  hot  water  and  steam  systems  with  regard  to 
the   position  and   manner   in   which   the   radiators  are   used. 

55.  State    the    distinguishing    features    and    the    advan- 
tages of  each  of  the  classes  in  question  54., 

56.  Classify   hot  water  and   steam  systems   with   regard 
to  the  method  of  pipe  connection  between  heat  generators 
and   the   radiators. 

57.  State  the  distinguishing  features  and  the  advantages 
of  each  of  the  classes  in  question  56. 

58.  Explain  the  difference  between  mercury  seal  vacuum 
systems    and    mechanical    vacuum    systems,    state    for    what 
buildings  each  is  best  adapted  and  give  advantage  of  each. 

59.  What  induces  the  flow  of  the  water  in  the  mains  and 
risers  of  a  hot  water  system? 

60.  Will    a    hot    water    heating    system    work    with    the 
source  of  heat  installed  in  the  attic?       Will  a  steam  system 
so  installed  work?     Why?     Give  reasons  in  each  case. 


j:6  HEATING  AND  VENTILATION 

CHAPTER  VII. 

61.  Classify  radiators  as   regards   materials. 

62.  Give  the  advantages  of  each  class  in  question  61  and 
show  to  what  use   each  class  is  particularly  adapted. 

63.  Classify  radiators  as  regards  form. 

64.  Show  what  difference  in  form  exists  between  a  steam 
radiator  and  a  hot  water  radiator. 

65.  In  general   which  is   the   more   efficient   radiator,   the 
high   one   or  the  comparatively  low  one?     Explain  why. 

66.  Explain  the  effect  of  the  surface  condition  of  a  rad- 
iator upon  its  heat  transmission  to  the  room  air. 

,67.  State  a  rule  for  finding  the  approximate  number  of 
sq.  ft.  of  surface  a  radiator  section  presents,  if  its  height 
and  number  of  columns  are  given. 

68.  State    the    limits    between   which    the    ratio    of   heat- 
ing  surface   to   grate   surface  in   hot   water  heaters   will   be 
found  to  vary. 

69.  Sketch  a  type  of  automatic  air  valve,  explain  its  use 
and   manner   of   working   and   show   where   placed   on    (1)    a 
steam    radiator,    (2)    a    hot   water    radiator. 

70.  Explain  the  use  of  an  expansion  tank.     Illustrate  by 
sketch  its  connection  and  relation  to  the  hot  water  system, 
and  give  an  approximate  rule  for  capacity  of  the  tank. 

CHAPTER    VIII. 

71.  What  is  the  average  rate,   in  B.   t.   u.   per  sq.   ft.  per 
degree  difference,   at   which   an   ordinary   cast   iron   radiator 
will  transmit  heat;   and  what  is   the   total   heat  transmitted 
per  hour  for   ordinary   hot   water  and   steam   radiators? 

72.  Room  temperature  is  70  deg.     Temperature  of  steam 
within    radiator    is    220    deg.      Show    the    derivation    of    the 
formula  R*  =   .004  IT. 

73.  The  living  room  in  problem  27  is  heated  by  hot  water 
radiation.     Average  temperature  within  radiator  is  170  deg. 
Determine   the    number   of   sq.    ft.    of   direct   radiation   which 
should  be  installed. 

;  74.  Calculate  direct  .steam  radiation  necessary  to  heat 
the  lecture  room  of  problem  29  if  the  temperature  of  the 
steam  within  the  radiator  is  225  deg. 

75.  What  is  the  transmission  constant  for  wrought  iron 
or  steel  pipe  as  commonly  used  for  green  house  radiation? 

76.  A  green  house  has  a  total  H  of  80000  B.   t.  u.     How 
many  feet  of  l1^  in.  pipe  should  be  installed  as  steam  radia- 
tion?    Steam  temperature  taken  at  225  deg.  and  house  tem- 
perature maximum  at   80   deg. 


QUESTIONS    AND    PROBLEMS  17 

77.  Prove  that  one  gallon  of  water  per  hour  entering  a 
radiator   at    180    deg.    and    leaving   at.  160    deg.    will    supply 
the  heat  radiated  by  one  sq.  ft.  of  surface  if  the  room  tem- 
perature  is   70    deg.,    i.   e.,    prove   that,    under   normal   condi- 
tions,   a    hot    water    radiator    requires    one    gallon    of    water 
per  is>q.  ft.   of  surface  per  hour. 

78.  Prove     that,     under    ordinary     conditions,    a    steam 
radiator  requires    .25  Ib.  of  steam  per  sq.   ft.   of  surface  per 
hour.      Steam    at    19    Ibs.    absolute.      Room    temperature    at 
70    deg. 

79     What  minimum  pitch  for  hot  water  mains  is  recom- 
mended?    For  steam  mains? 

80.  Along  what  walls,    (exposed  or  unexposed)   are  rad- 
iators  usually   placed  and   why? 

81.  In   buildings    of  several   stories   why   is   it   desirable 
to  arrange   the   radiators   in   tiers   vertically,   one   above   the 
other? 

82.  Show  in  what  manner  the  expansion  and  contraction 
of    a    long    riser    may    be    accommodated    by    the    horizontal 
connection  to  the   radiators. 

83.  Assuming    your    own    values    of    cost£    of    coal,    fur- 
nace efficiency,  etc.,   show  the   radiation  loss   in  B.   t.   u.  and 
the  accompanying  expense   for  fuel   Loss   in  leaving  a  50  ft. 
stretch    of    6    in.   -steam   main,    carrying   5   Ibs.    pressure,    un- 
insulated  for  one  year. 

84.  What  is  water  hammer?     Explain  precautions  which 
will   avoid   it. 

85.  In   how  many  ways   may  the   condensed   water   of  a 
steam    system    be    returned   to    the    boiler? 

,86.     Explain    each    method    in    question    85.      'Show    when 
each   is   preferable  and  give   the  advantages  of   each. 

87.  In   general,    what   different   type    of   valve   would   be 
specified  for  hot  water  systems  as  compared  with  that  spe- 
cified  for  steam   systems,   and   why? 

88.  Why  are  green  houses  almost   invariably  heated  by 
pipe  coils  instead  of  ordinary  cast  iron  radiators? 

89.  In   hot   water  heating  are   separate   mains   ever  run 
to   groups    of   risers?     What   advantage    would   this   present 
over  taking  all   the   risers   from   one   common   main?     With 
what  type  of  <boiler  is  this  arrangement  usually  employed? 

90.  Compare  advantages  and   disadvantages    of   the   one 
pipe  and  the  two  pipe  hot  water  system. 

91.  Explain    the    fundamental    piping    difference    which 
exists   in  a  one  pipe  hot  water  system  as   compared  with  a 
one  pire  steam  system. 


18  HEATING   AND    VENTILATION 

92.  Compare    radiators    as    to    position    of    tappings    for 
different   systems    of   hot   water   and    steam   heating. 

93.  How  many  valves  should  be  used  And  where  placed, 
for  each  radiator  in  a  hot  water,  two  pipe  system;  in  a  two 
pipe  steam  system? 

94.  Explain  the  various  'methods  of  taking  up  expansion 
in   mains;    in   branches |    in   risers. 

95.  Explain  (the    different   methods    of    insulating    steam 
and  hot  water  pipes  from  loss  of  heat. 

CHAPTER   IX. 

96.  Name  some  advantages  to  toe  gained  by  the  applica- 
tion  of  vacuum   systems   to   steam  heating   systems. 

97.  Into  what  two  general  classes  may  vacuum  systems 
be    divided   with   regard   to    the   manner    of   maintaining   the 
vacuum?     Compare  the    differences   and    discuss   the   proper 
field  for  each   system. 

98.  Name  some  methods  by  which  the  vacuum  is  main- 
tained   in   a    mechanical    vacuum    system. 

99.  Explain  the  manner  in  which  a  mercury  seal  vacuum 
system    operates. 

100.  Distinguish  between  the  Webster  and  the  Paul  sys- 
tems. 

101.  Sketch  a  typical  layout  of  a  mechanical  vacuum  sys- 
tem,  showing  complete   connections   of   the   various   auxilia- 
ries. 

102.  Discuss    the    principles    upon    which    the    expansion 
stem  valves   and   the   float   valves   operate. 

103.  Explain   the    use    of   screens   and   strainers,    describe 
them  and  state  where  located  when  applied  to  vacuum  sys- 
tems. 

104.  Explain  the  use  of  the  water  spray  and  state  where 
located    on   the   system. 

105.  Describe    the    governing    device    commonly    used    on 
•such   systems  and   show  how  connected   up. 

106.  Discuss  the  use  of  the  pump  with  a  steam  actuated 
yalve  -as  compared  to  the  pump  with  a  mechanically   oper- 
ated valve. 

107.  Describe  the  automatic  feature  in  the  Marsh  pump. 

CHAPTER  X. 

i/ 

108.  What   one   great  advantage   has   the   plenum   system 
over  any  other  system   of  heating? 

109.  Name    the    essential    elements    composing    a    plenum 
system. 


QUESTIONS    AND    PROBLEMS  19 

110.  In   what    manner    may   a   plenum   .system    be    used    to 
cool   a   building? 

111.  What  two  methods  of  installing  a  mechanical  warm 
air   system   may   be    employed,    having   special    reference    to 
position  of  fan  ,and  ooils? 

112.  Give    the    advantages    and    disadvantages    of    each 
method  in  question  111. 

113.  Explain  how  a  fan  for  exhaust  work  differs  in  me- 
chanical  construction   from  one   used  for  plenum  work. 

114.  W'hat    four   methods    of    driving    exhaust   or    plenum 
fans  are  common?     Which  preferred? 

115.  Distinguish  between  a  full-housed  fan  and  a  three- 
quarter  housed  fan. 

116.  What  two  kinds  of  plenum  heating  surfaces  are   in 
common   use? 

117.  Explain  how  each  kind  of  plenum  heating  surface  is 
made  up  and  give  the  advantages  of  each  construction. 

'  118.  As  regards  installation,  into  what  two  parts  is  the 
total  heating  surface  of  a  plenum  system  usually  divided? 
What  position  do  these  parts  take  with  respect  to  the  fan? 

119.  Show  by  sketch  the  difference  between  a  single  duct 
and  a  double  duct  plenum  .system. 

120.  State  the   advantages   and  the   disadvantages   of  the 
double  duct  and  the  single  duct  systems. 

121.  Name  the  parts  essential  to  a  mechanical  air  wash- 
ing and  humidifying  system  and  state  the  position  of  each 
relative   to  the   others. 

122.  Explain  how  washing  the  air  cools  it. 

CHAPTER  XI. 

123.  For  the  design   of  plenum  systems,   what  air  veloc- 
ities are   allowable    in   the   following   places, — fresh    air    in- 
take,  over  coils,   main  duct  at  fan,   stacks,   registers? 

124.  (a)   Does  K,  the  rate  of  transmission  from  a  plenum 
heating   'Surface,    increase    or    decrease    as    the    air    velocity 
over'  the   .surface    increases? 

(b)   Does  the  average  K  increase  or  decrease  as  the 
number  of  sections  in  depth  is  increased? 

125.  Why    do    the    first    rows    of    pipe    in    a    coil    plenum 
heater,    or  the   first   sections   in  a   cast  plenum   heater  con- 
dense more  steam  than  other  rows  or  isections? 

126.  (a)   W'hat  are  commonly  taken  as  the  minimum  and 
maximum  limits  to  the  number  of  pipes  in  depth  in  design- 
ing a  coil  plenum  heater? 


20  HEATING    AND    VENTILATION 

(b)  What  are  the  similar  limits  to  the  number  of  sec- 
tions in  depth  in  designing  a  cast  iron  plenum  heater? 

127.  If    the    average    transmission    constant,    K,    is    8.5, 
steam  temperature   227   deg.,    minimum   outside   temperature 
—   10    deg.   and   temperature    leaving   heater    140    deg.,    what 
number   of   B.    t.    u.    is    one    sq.    ft.    of   the    heater    delivering 
per   hour? 

128.  The  auditorium   of  the   opera   house   in   problems   30, 
31  .and  33,  is  provided  with  direct  radiation  sufficient  to  sup- 
ply   the    heat    loss,    H,    from    the    building.    In    addition,    two 
plenum    systems    furnish    the   air    for    ventilation,    which    is 
heated    to    70    deg.    miaximum.      Assuming-,    as    before,    the 
minimum   outside   temperature   as   —   20    deg.,    calculate    the 
total    sq.    ft.    of    coil    plenum    heating    surface    which    should 
be  installed.     K  =  8.5.     Steam  at  5  Ibs.  gage. 

129.  In   problem   128   a   cast   iron  heater   is   installed   with 
an  air  velocity  over  coils  of  approximately  1500  ft.  per  min. 
Using  Tables  XIX  and  48  design  the  heater. 

130.  Design,  as  in  problem  129,  the  heater  for  the  theater 
building  if  pipe  heater  be   used   instead  of  the  cast  heater. 
Use    Table   XVIII. 

131.  (a)  In  problem  128  show  how  many  pounds  of  steam 
would  be  condensed  per  hour  by  the  plenum  systems? 

(b)   At  what  average  rate  per  sq.  ft.  of  surface   per 
hour? 

CHAPTER    XII. 

132.  From    the    fundamenal    equation,    v    =    \/2gh^  show 
the    derivation    of    the    approximate    general    rule    that    the 
theoretical    velocity    of    dry    60    deg.   air,   when    its    pressure 
is   measured   by  a   water   column   gage    in    inches    of   water, 
equals  sixty-six  times  the  square  root  of  the  water  column 
reading  in  inches,  or  that  v  =  66  \fhw. 

133.  By  what  action  at  the  orifice  is  this  theoretical  dis- 
charge  reduced? 

134.  In  problem   128   each   fan   handles    2250000    cu.    ft.    of 
air   per   hour   through  a   duct   in   which   the   pressure    is    .75 
oz.  per  sq.   in.     What  theoretical  horse-power  is  necessary? 

135.  In  problem  134  if  the  efficiency  of  the  fan  is  25   per 
cent.,  what  will  be  the  actual   horse-power  of  the  fans  in- 
stalled? 

136.  If  the  fans  in  problem  135  are  run  by  steam  engines 
using   32   Ibs.    of   steam   per   H.    P.    hour,    how   many   pounds 
of  dry  steam,  in   excess   of   the   engine   exhaust,   will   be   re- 
quired by  the  plenum  heaters  per  hour?     Use  heat  loss  due 


QUESTIONS    AND    PROBLEMS  21 

to  ventilation  as  calculated  in  problem  33.  Exhaust  steam 
equals  85  per  cent,  heating  value  of  dry  steam.  Take  engine 
horse-power  at  4-3  fan  horse-power. 

137.  The    fans    installed    for    problem    136    shall    have    a 
speed  of  approximately  175  r.  p.  m.     Determine   their  diam- 
eters by  Carpenter's  formula  and  check  .by  Table  50. 

138.  With    data    of    problems    136    and    137,    calculate    ap- 
proximate   cylinder   dimensiors    for   engines,   if   steam   pres- 
sure is  100  Ibs.  per  sq.   in.  by  gage,   back  pressure  is   5   Ibs. 
gage   and   r  —   3. 

139.  Show   the   layout   of   piping   used   to   connect   a   back 
pressure  valve  to  a  plenum  system  and  explain  the  function 
of  the  valve. 

140.  (a)  Under  what  conditions  does  a  fan  deliver  air  at 
practically    the    same    velocity    with    which    the    blade    tips 
travel? 

.(b)  To  what  extent  is  this  velocity  reduced  when  a 
fan  is  connected  ito  a  system  of  ducts  and  why? 

141.  (a)    If   a   fan   has    its    free    discharge    opening  closed 
by  a   gate   and   while    running   full    speed    this   gate   is   sud- 
denly opened,   what  change  In   speed  will   be   noticed  at   the 
instant  of   opening?     Why? 

(b)  What  change  in  the  horse-power  of  the  prime 
mover  will  be  noticed  at  instant  of  opening?  Why? 

CHAPTER    XIII. 

142.  (a)    What    two    kinds    of    centralized    heating    plants 
are  in  use? 

(b)  Which  type  would  you  select  for  a  very  hilly 
city  or  for  very  high  buildings  and  which  for  a  comipara- 
tively  levdl  city'  with  low  buildings?  Why? 

143.  Compare  the  two  kinds  of  central  heating  plants  as 
regards   (1)   first  cost,    (2)    operation  cost,    (3)    regulation. 

144.  Describe  some  types  of  conduits  used  in  central  sta- 
tion  work. 

145.  (a)   In  a  long  straiigftit  heating  main  of  a  hot  water 
system    how    many    inches    expansion    would    you    expect    in 
100   feet   of  pipe,  if  temperature   extremes   were   0   deg.   and 
200   deg?     Prove   it. 

(b)  About  what  distance  apart  would  you  install 
expansion  joints? 

146.  How  are  pipes  supported   in  conduits? 


22  HEATING    AND    VENTILATION 

147.  How  and  why  are  pipes  "anchored"  at  certain  points? 

148.  Describe  some  types  of  expansion  joints  and  explain 
the  advantages   of  each. 

149.  How  are  service  connections  miade  to  conduit  'mains? 

150.  Show  wlhat  is  meant  by  a  power  chart  and  of  what 
use  it  is  to  the  central  station  engineer. 

151.  Under  what  conditions  might  exhaust  s-team  be   su- 
perheated? 

152.  What  two  types  of  hot  water  central  station  plants 
are  in  use? 

153.  In   general,  'how   many  sq.   ft.    of  radiation   will!   the 
average    business    block    furnish?      The    average    residence 
block? 

154.  A  hot  water  'Central   station   has   the   highest   radia- 
tion,  300  ft.  above  the  station  floor.     What  is  the  pressure 
in  the  mains  at  the  floor  level   of  the   station? 

155.  In  a  hat   water   system,   what   causes   the    difference 
in  pressure   between  the   outgoing  and   the   incoming  main? 
In  practice  about  wlhat  is   this   difference? 

156.  (a)   A  conduit   of   a   double   main   hot   water  heating 
system  is  800  ft.  long  and  at  the  far  end  supplies  an  office 
building  of  50000  sq.  ft.   of  radiation.     Find  the  differential 
pressure  at  the  pumps  dofe  to  friction   in  the  conduit  pipes, 
if  the   velocity   therein   is   8.5   ft.   per   sec.     Use   formula   70 
with  0  =    .022. 

(b)  With  all  conditions  the  same,  calculate  as  in  (a), 
if  the  velocity  is  4  ft.  per  sec. 

157.  Show  what   number   of  sq.   ft.   of  district  hot   water 
radiation  can  be  supplied  per  pound  of  exhaust  steam  on  a 
zero  day. 

158  In  the  plant  indicated  in  problem  156,  find  the  amount 
of  beating  surface  in  the  reheater  tubes  if  one  pound  of 
steam  gives  heat  for  4  sq.  ft.  of  radiating  surface  for  one 
hour. 

159.  Determine   the    indicated   horse-power   of  the   circu- 
lating  pump    necessary   in    problem    156    for    each    condition 
of  velocity,  if  the  efficiency  is  65  per  cent,  and  the  loss  due 
to  friction  and  head  in  the  building  is  equivalent  to  an  ad- 
ditional head  of  55  Ibs. 

160.  Describe   a   high   pressure   steam   heater   for   central 
station  hot  water  systems  and  state  where  and  how  usually 
installed. 

161.  What  advantages  are  gained  by  having  a  number  ot 
circulating   pumps   rather  than   one. 


QUESTIONS    AND    PROBLEMS  23 

162.  Compare  centrifugal  pumps  and  reciprocating  pumps 
for    central    station    circulating    work. 

163.  Explain     how     steam     boilers     may     be      used      as 
heating  boilers   in  a  central  station   heating  plant. 

164  A  100  H.  P.  boiler  will  supply  on  an  average  16000 
sq.  ft.  of  hot  water  radiation.  Prove  It. 

165.  With  coal   of   13000   B.   t.   u.   value   and   costing   $2.00 
per    ton    of    2000    Ibs.,    calculate    the    cost    of    supplying    one 
sq.    ft.    of   water   radiation    one    season   of    7    months    if    the 
average  outside  temperature  is  32   deg.     Calculate  the  same 
for  a  season   of  8   months  with  an  outside  average  temper- 
ature of  32  deg. 

166.  In  what  two   ways  may  heat  regulation   be   effected 
in   a    hot   water    central    station    system? 

.167.  If  the  plant  in  problem  156  lhad  been  a  steam  plant 
instead  of  a  hot  water  plant  and  the  exhaust  steam  available 
was  that  given  by  a  500  Hi  P.  city  water  pump  at  the  rate 
of  35  Ibs.  per  horse-power  hour,  show  how  much  auxiliary 
steam  would  be  needed  per  hour  for  heating,  Exhaust  at 
5  Ibs.  gage. 

168.  (a)  Determine  the  size  of  the  steam  supply  main  in 
problem  167,  if  the  pressure  at  the  power  house  is  5  Ibs. 
gage  and  a  drop  of  not  more  than  one  pound  is  allowed 
at  the  entrance  of  the  main  to  the  heated  building.  Table 
36  gives  the  pounds  of  steam  per  min.  that  may  be  safely 
allowed.  .See  Art.  175. 

(b)   Recalculate   (a)    if  the  maximum  drop  allowable 
is  8  oz. 

,169.     Explain   the  action  of  pressure  reducing  valves. 

170.  How  is  exhaust  steam  purified  for  use  in  the  service 
main? 

CHAPTER    XIV. 

171.  Name  two   ways   in  which   temperature   control   sys- 
tems may  reduce  heating  expense. 

172.  In  what  ways  would  the  temperature  control  for  a 
small  plant   (say  a  small  residence)   differ  from  the  control 
system  of  a  large  plant? 

173.  What  power  medium  for   opening  or   closing  valves 
is   most   commonly   used   in   temperature   control   systems? 

174.  In  what  particulars  do  the  Johnson,  Powers  and  the 
National  regulating  systems  differ? 

175.  Name  the  important  parts  of  any  regulating  system 
and  explain  the  function  of  each. 


24  HEATING    AND    VENTILATION 

176.  W.hat  method   is   commonly   used   for   furnishing   the 
air  pressure  used  in  regulating  systems? 

177.  Within  what  maximum  number  of  degrees  of  fluctu- 
ation   should    a    good    regulation    system    control    the    tem- 
perature? 

CHAPTER    XV. 

178.  What   objection  against  heating  by  electricity   prac- 
tically  prohibits   its   use? 

179.  Show  what  the  energy  of  one  watt  hour  is  equal  to 
in   terms  .of  B.   t.   u.   per  hour. 

180.  One    watt    hour    absorbed    in    an    electric    radiator 
would  equal  the  heat  delivered  by  how  many  sq.   ft.   of  hot 
water   radiation? 

CHAPTER  XVI. 
PROBLEMS  IN  REFRIGERATION. 

181.  (a)      Into    what    two    groups    may    all    refrigerating 
processes  be  classified? 

(b)  Which   group   is   the   more   practical    for   opera- 
tions on  a  large  scale? 

(c)  Name    four    different    mechanical    refrigerating 
systems. 

182.  (a)     .Describe    the    vacuum    system    of    refrigeration, 
(b)     In   what  manner   is   the  absorption  of  heat  ac- 
complished in  the  vacuum  system? 

183.  Name  the  four  principal  parts  of  the  complete  cycle 
of  the  cold  air  refrigeration  system  and  explain  the  appara- 
tus each  part  requires. 

184.  Name  three  refrigerants.     Which  one  is  the  most  com- 
monly .used  and  why? 

185.  In  what  ways  are  the  compression  and   the  absorp- 
tion systems  of  refrigeration  similar? 

186.  (a)     Describe,   in  order,   the  cycle  of  changes  which 
the  ammonia  gas  passes  through  in  a  compression  system. 

(ib)     Name,  in  .order,  the  pieces  of  apparatus  through 
which  the  ammonia  circulates. 

187.  (a)      Describe    two    types    of    ammonia    compressors, 
(b)     What   structural   differences  distinguish  a   car- 
bon dioxide  compressor  from  an  ammonia  compressor? 


QUESTIONS    AND    PROBLEMS  25 

188.  (a)     'What  four  types  'of  condensers  are  in  use  with 
compression  systems? 

(b)     Describe  each  and  note  differences. 

189.  Name  and  describe  the  two  classes  of  brine  coolers. 

190.  What    property    of    ammonia    makes    the    absorption 
s*ystem  of  refrigeration  a  possibility?     With  ;how  many  dif- 
ferent refrigerants  may  the  absorption  system  be  operated? 

191.  In    the   absorption  .system,    what    corresponds   to    the 
compressor  used  in  the  compression  system? 

192^  Draw  diagrammatic  representations  of  the  cycles  of 
the  compression  and  absorption  systems  and  compare  the 
two  cycles. 

193.  Name  and  describe  the  use  of  those  pieces  of  absorp- 
tion apparatus  which  the  compression  system  does  not  use. 

194.  In   what   two    ways   may   the    refrigerating   effect  of 
either    system    be    delivered    to    rooms    or    to    water    for    ice 
making? 

195.  What    three    arrangements    of    refrigerating    surface 
may  be  used  for  maintaining  low  temperatures  in  storage  or 
other  rooms? 

196.  With  the  plenum  system  of  maintaining  low  storage 
temperatures,    state   the   difficulties  caused   by   the   moisture 
in  the  air,  and  describe  methods  for  overcoming  these  diffi- 
culties. 

197.  Describe  the  method  of  central  station  refrigeration. 


•> :  V-:V*  CHAPTER  XVII. 

198.  (a)      Define   the   unit  of  refrigerating  effect   (the  ton   of 
refrigeration)  and  show  the  numiber  of  B.  t.  u.  it  represents. 

(b)  A  one-ton  refrigerating  plant  is  capable  of  ab- 
stracting how  many  B.  t.  u.  per  hour?  If  a  brine  coil  is 
absorbing  600000  B.  t.  u.  per  hour,  what  refrige'ration  capa- 
city does  the  coil  represent? 

199.  .What  four  sources  of  heat  supply  to  a  refrigerating 
system  should  be  taken  account  of  dn  calculations  of  refrig- 
erating capacity? 

200.  A  cold  storage  room  is  75'  x  125'  and  12'  ceiling.    With 
no  windows,  and  no  allowances  for  ventilation  or  door  open- 
ing, find  the  refrigerating  capacity  of  a  machine  to  supply, 


26  HEATING    AND    VENTILATION 

by  direct  coils,  the  refrigeration  loss  throug-h  the  roof,  floor 
and  walls  of  this  room:  — 

(a)  If  maintained  at  0°   F.,   and   insulated  with   12" 
mill  shavings. 

(b)  If  maintained  at  30°   F.,   and  insulated  with   6" 
mill   shavings.  • 

Roof  and  walls  insulated  the  same  in  each  case. 
Take  refrigeration  loss  through  the  insulated  floor  as  one- 
half  the  loss  through  equal  wall  or  roof  area. 

201.  (a)     If    two   such    rooms   as    in    problem    200,    b,    are 
cooled  by  the  plenum  system,  and  the  air  is  changed  'three 
times    eve>ry    hour,    find    the    refrigerating    capacity    of    the 
machine  necessary  under  these  conditions:  — 

Outside  temp.  =  100°,  and  85%  humidity. 

Temp,  of  air  flowing  into  rooms  =  ?  Take  brine 
temperature  0  degrees  entering  coils,  and  10  degrees  leav- 
ing. Coils  arranged  to  prevent  freezing  on  their  exterior 
surface. 

(<b)  WThat  would  be  the  relative  humidity  in  the 
rooms? 

202.  In  problem  200,  a,  what  would  be  the  length   of  the 
ll/2   inch  direct  >cooling  coils? 

203.  In  problem  201,  determine  the  surface  of  the  plenum 
cooling  coils. 

i204.  A  banking  room  is  cooled  .by  the  circulation  of  brine 
through  plenum  codls.  A  test  of  the  plant  gave  the  follow- 
ing data:  — 

Cubic  feet  in  room,  85000.     Air  changes,  4  per  hour. 

Cooling  surface  of  coil,  526  sq.  ft. 

Outdoor  temp.,   84^°,   humidity,    68%. 

Brine  to  coils,   37^°,  from  coils,   40%°. 

Incoming  air  cooled  down  to  66°. 

Ave.    temp,    in   banking   rooms,    77%°,   irel.    humidity. 


Frozen  moisture  allowed  to  collect  on  coils  during 
day. 

What  refrigerating  capacity  of  the  machinery  does 
this  performance  indicate  if  the  installation  were  100%  effi- 
cient? 


QUESTIONS  AND  PROBLEMS  27 

205.  With  the  data  given  in  204,  calculate  the  heat  trans- 
mission at  the  coils  per  sq.  ft.  per  hour  per  degree  difference, 
(Compare  with  Art.  212). 

206.  (a)     An  ice  making  plant  circulates  calcium  brine  of 
22°    Baume  density.     What  is  the  value  of  a  gallon  degree  at 
this  plant? 

(b)  If  this  plant  is  one  of  50  tons  capacity,  express 
the  capacity  in  terms  of  gallon  degrees.      (See  Table  60). 

(c)  If    the    brine    into    freezing   tank    registers    12° 
and   leaving  tank   registers   18°   find    number   of   gallons   cir- 
culated per  minute. 

207.  An    ice    making    plant    circulates,    per    minute,    300 
gallons'  of  22°    Baume   calcium  brine,   which   enters  freezing 
tank  at  11°  and  leaves  at  18°.     Find  the  tonnage  capacity  of 
the  plant. 


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WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  5O  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


NQV   25  1932 
AUG  11  &S43 


LD  21-50m-8,-32 


YB  5 1 956 


